A Thesis Entitled Exposure Evaluation and Control of Acetone in A

A Thesis entitled Exposure Evaluation and Control of Acetone in a Plastination Laboratory by Skylar Rohrs Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Occupational Health

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Dr. Sheryl Milz, Committee Chair

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Dr. Michael Valigosky, Committee Member

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Dr. Carlos Baptista, Committee Member

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Dr. Patricia R. Komuniecki, Dean College of Graduate Studies

The University of Toledo May 2014

This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author.

An Abstract of

Exposure Evaluation and Control of Acetone in a Plastination Laboratory

Skylar Rohrs

Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Occupational Health

The University of Toledo

May 2014

Occupational exposure monitoring to acetone was conducted in a university laboratory. The lab specializes in the process of plastination, a unique method involving specimen preservation. Exposure to acetone occurs during the dehydration and transferring of specimens from large, open-top vats of acetone. This study evaluated four different ventilation systems to determine the most effective method for removing acetone vapors and reducing occupational exposures below acceptable occupational exposure limits. General ventilation, increase in negative pressure in general ventilation, and two local exhaust ventilation systems were evaluated. The results indicated a slotted hood with dedicated exhaust and supply fan was the most effective at reducing exposure and removing acetone vapors from the location. The final method was determined to be the most effective at reducing chemical exposure and eliminating potentially explosive atmospheres.

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I would like to dedicate this work to my family and friends for their constant love and support. Without you all continuously being there for me, I may have finished this paper a tad bit sooner, but it wouldn’t have been as entertaining.

Acknowledgements

I would like to acknowledge the following for their willingness to help and dedicate their time to make this work possible; Dr. Michael Valigosky, Heather Lorenz, and the entire Environmental Health and Radiation Safety Staff at the University of

Toledo for their guidance and assistance in the research; Dr. Carlos Baptista for introducing me to this exciting process known as Plastination; and my major advisor Dr.

Sheryl Milz for helping organize the study.

Table of Contents

Abstract ...... iii

Acknowledgements ...... v

Table of Contents ...... vi

List of Tables ...... ix

List of Figures ...... x

List of Abbreviations ...... xi

List of Symbols ...... xiii

1 Introduction…...... 1

1.1 Overview ...... 1

1.2 Statement of Problem ...... 3

1.3 Purpose and Significance ...... 3

1.4 Hypotheses ...... 4

1.5 Objectives ...... 4

2 Literature Review ...... 5

2.1 Plastination ...... 5

2.1.1 History of Plastination ...... 5

2.1.2 Methods of Plastination ...... 6

2.2 Acetone … ...... 7

2.2.1 Properties of Acetone ...... 8

2.2.2 Temperature and Volatility ...... 8

2.3 Exposure Guidelines ...... 8

2.4 Flammable Liquids, Flash Points, Explosive Range ...... 9

2.5 Health Effects of Acetone Exposure ...... 10

2.5.1 Short-Term Exposure ...... 11

2.5.2 Long-Term Exposure ...... 12

2.6 Hazard Evaluation ...... 12

2.7 Hazard Control ...... 13

2.8 Ventilation in a Laboratory Setting ...... 14

2.8.1 General Exhaust ...... 14

2.8.2 Local Exhaust...... 14

2.8.2.1 Hoods in Exhaust Systems ...... 15

2.8.2.2 Hood Design ...... 15

2.9 Administrative Controls ...... 17

2.10 Personal Protective Equipment ...... 17

2.11 Summary ...... 18

3 Materials and Methods…...... 20

3.1 Overview ...... 20

3.2 Location ...... 21

3.3 Initial Lab Ventilation Room 1400G ...... 22

3.4 Sampling Areas and Times ...... 22

3.5 Equipment and Supplies ...... 23

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3.6 Sampling Procedures and Data Collection ...... 24

3.6.1 Pre-Calibration of MiniRae 2000...... 24

3.6.2 Sampling and Data Collection ...... 25

3.6.3 Post-Sampling Data Collection ...... 26

4 Results…...... 27

4.1 Overview ...... 27

4.2 Dilution Ventilation in Room 1400G ...... 27

4.3 Adjusted Dilution Ventilation in Room 1400G ...... 28

4.4 Local Exhaust Ventilation Slotted Hood #1 in Room 1400G ...... 29

4.5 Local Exhaust Ventilation Slotted Hood #2 in Room 1400B ...... 31

5 Discussion…...... 33

5.1 Overview ...... 33

5.2 Limitations ...... 36

5.3 Recommendations for Future Studies ...... 37

5.4 Conclusions ...... 37

References …………...... 39

A Laboratory Layouts ...... 43

B Dilution Ventilation in Room 1400G 11/26/12 Results ...... 47

C Adjusted Dilution Ventilation in Room 1400G 12/21/12 Results ...... 50

D Local Exhaust Ventilation Slotted Hood #1 in Room 1400G 10/18/13 Results....53

E Local Exhaust Ventilation Slotted Hood #2 in Room 1400B 3/10/14 Results ...... 57

F Slotted Hood #1 Picture and Measurements ...... 60

G Slotted Hood #2 Picture and Measurements ...... 61

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List of Tables

3.1 MiniRAE 2000 Acetone Correction Factor and Alarm Settings ...... 25

4.1 Dilution Ventilation in Room 1400G 11/26/12 Results ...... 28

4.2 Adjusted Dilution Ventilation in Room 1400G 12/21/12 Results ...... 29

4.3 Local Exhaust Ventilation Slotted Hood #1 in Room 1400G 10/18/13 Results....30

4.4 Local Exhaust Ventilation Slotted Hood #2 in Room 1400B 3/10/14 Results ...... 32

5.1 Summary of Lab Data and Calculated Time Weighted Averages for Acetone .....34

List of Figures

3-1 MiniRae 2000...... 24

4-1 Slotted Hood #1 in Room 1400G...... 30

4-2 Slotted Hood #2 in Room 1400B ...... 31

A-1 Laboratory 1400G Layout and Square Footage ...... 43

A-2 Initial Laboratory 1400G Arrangement ...... 44

A-3 Pre-Alteration Ventilation in Laboratory 1400G ...... 45

A-4 Laboratory 1400B Layout and Square Footage ...... 46

F-1 Slotted Hood #1 Picture and Measurements ...... 60

G-1 Slotted Hood #2 Picture and Measurements ...... 61

List of Abbreviations

ACGIH ...... American Conference of Industrial Hygienists AVG ...... Average

CFR ...... Code of Federal Regulations

FPM...... Feet Per Minute

HVAC ...... Heating Ventilation and Air Conditioning

IDLH ...... Immediately Dangerous to Life or Health

LEL ...... Lower Explosive Limit LEV ...... Local Exhaust Ventilation mmHG...... Millimeter of Mercury

NFPA ...... National Fire Protection Association NIOSH ...... National Institution of Occupational Safety and Health

OEL ...... Occupational Exposure Limit OSHA ...... Occupational Safety & Health Administration

PEL ...... Permissible Exposure Limit PEL-TWA ...... Permissible Exposure Limit-Time Weighted Average PID ...... Photo Ionization Detector ppm ...... Parts Per Million

REL ...... Recommended Exposure Limit

SCBA ...... Self Contained Breathing Apparatus STEL ...... Short-Term Exposure Limit

TLV ...... Threshold Limit Value TLV-STE ...... Threshold Limit Value- Short Term Exposure Limit TLV-TWA ...... Threshold Limit Value- Time Weighted Average TWA ...... Time Weighted Average

UEL ...... Upper Explosive Limit

VOC ...... Volatile Organic Compound

xii

List of Symbols

% ...... Percent

°C ...... Degrees Celsius

xiii

Chapter 1

Introduction

1.1 Overview

Specimen preservation has varied over centuries and has recently become an occupational exposure concern from exposure to preservatives used throughout the process. A plethora of studies have been conducted assessing the exposure of students and faculty to formaldehyde in gross anatomy labs. The problem occurs during dissection and handling of formalin preserved tissue used as teaching aides. Not only is formaldehyde an irritant gas that shows effects of dermatitis and asthma, but is also included in the list of known carcinogens. The primary route of exposure is through inhalation, where it is absorbed by the lungs and delivered to other organ systems. Many studies have shown over-exposure to formaldehyde during gross anatomy labs. A study was conducted in a gross anatomy teaching lab where personal samples were collected and showed Time Weighted Averages (TWAs) up to 4.0 parts per million (ppm) (Demer et al.,1996). The results confirmed 29% of samples far exceeded the OSHA action limit of 0.5 ppm, and 58% of the samples exceeded the OSHA STEL of 2 ppm (Demer et al.,

1996). According to Ohmichi, people working in close proximity to cadavers preserved with formaldehyde have a possibility of being exposed 2 to 3-fold higher than the mean

1 concentration of indoor formaldehyde (2006). Because of this risk, other processes were developed to preserve specimens.

The most recent preservation process, plastination, was developed by Dr. Gunther von Hagens in 1977. This development allowed for the treatment of every part of the body to preserve it as a hard plastic with a naturalistic look (Khullar et al., 2012). This new process was revolutionary by helping to eliminate the need of using formaldehyde as a fixative to maintain a life-like state for educational purposes. Students and faculty are now able to handle and observe body specimens in a realistic state without exposure to formaldehyde.

The process of plastination, which replaces water and fat in a specimen with a silicone product, is similar amongst different researchers, but can vary slightly. The process uses an intermediary organic solvent (typically acetone) that dehydrates the specimen (DeJong et al., 2007). Multiple acetone baths are used and most contain acetone that is above 80% purity (Henry, 2007). The solvent is then removed from the tissue

(using a series of pressure reductions by vacuum) causing a void in the cells (Henry,

2007). These voids are then impregnated with a polymer-mix. The biological specimens are cured and then allowed to dry.

Organic vapor exposure has been extensively studied in the work-place setting. A considerable amount of evidence suggests that long-term occupational exposure to organic vapors has detrimental effects on the central nervous system, causing cognitive diminishing, and a variety of other moderate to serious impairments (Daniel et al., 1999).

One such organic vapor is acetone. Acetone is naturally produced in the environment and

2 in the human body. It is quickly absorbed by the body through inhalation, dermal exposure, and ingestion, making it an occupational health concern when used in large amounts or with high concentrations. Occupational health professionals must determine adequate control measures to eliminate exposure above published OEL’s and other associated risks.

1.2 Statement of Problem

Scientific research has proven that organic vapors, such as acetone, present a potential inhalation risk as well as other occupational concerns. Acetone is a fire hazard when vapor from large vats used in the plastination process approach the lower explosive limit. Health effects from overexposure to acetone range from moderate irritation to severe central nervous system depletion (AEGLs, 2005). Although many studies have been designed to determine the effects of occupational exposure to organic solvents, there is a lack of published data on acetone exposure and hazard control enhancement during the plastination process.

1.3 Purpose and Significance

The purpose of this study is to conduct an industrial hygiene air sampling investigation in a plastination laboratory, develop appropriate exposure controls, and evaluate their effectiveness. Providing the information from this study to other occupational health professionals will aid in the development of proper techniques, which are necessary when working in plastination laboratories.

1.4 Hypotheses

The hypotheses tested include:

1. The measurement of airborne acetone concentration in the breathing zone of

workers will not exceed the OSHA PEL of 1000 ppm during the plastination

process.

2. The measurement of airborne concentration of acetone in the general area within

the procedural rooms will be above the Lower Explosive Limit (LEL).

3. The installation of a local exhaust ventilation system will decrease the measured

level of acetone in the breathing zone of workers.

4. The installation of a local exhaust ventilation system will lower the concentration

of acetone below the Lower Explosive Limit (LEL).

1.5 Objectives

The objectives of this study are to:

1. Determine external occupational exposure of acetone to laboratory personnel

involved in plastination process.

2. Determine if existing ventilation is adequate to control exposure to acetone

vapors.

3. Compare the previous ventilation designs to the modified ventilation designs.

4. Assess external occupational exposure of acetone to laboratory personnel

involved in plastination process after modified ventilation.

Chapter 2

Literature Review

2.1 Plastination

The process of plastination is now the benchmark when it comes to preservation of biological specimens for use in educational settings. Not only is it used for research, anatomy, pathology, and clinical studies, but often referred to as art.

2.1.1 History of Plastination

Plastination is a process first introduced by the German Scientist, Gunther von

Hagens. The basic principle of plastination is to preserve biological tissues, organs, or entire bodies and replace their fluid with a curable polymer. Gunther von Hagens developed this process during 1977 in an attempt to improve the quality of renal specimens (Khullar et al., 2012). Not only was this a groundbreaking process necessary to help preserve specimens for an extended amount of time, but it also eliminated risks associated with the handling and exposing of formalin preserved specimens to individuals studying anatomy and pathology. Gunther Von Hagens’ basic ideabehind plastination is,

“in order to make a specimen permanent, decomposition must be halted” (Khullar et al.,

2012). Formalin can delay the decaying process, but does not prevent it. This makes plastination valuable as it stops the progression of decay, and can make a specimen last almost indefinitely.

2.1.2 Methods of Plastination

The process begins by collecting the specimen of choice. Choosing a specimen with the shortest postmortem interval is best because the tissues haven’t begun to decay.

Often times the bodies can be preserved in formalin to help slow down the degeneration process until plastination is available. The formalin is required to be removed by submerging the specimen in an acetone and hydrogen dioxide bath for 7 days. After 7 days, it needs to be rinsed with water, and then re-submerged in acetone (Dejong et al.,

2007).

The next step is to replace bodily fluids with acetone. This process is known as

Dehydration. Other solvents, such as alcohols and methylene chloride, do not possess the same chemical characteristics as acetone (such as miscibility in water) making it the most desirable solvent used during plastination (DeJong et al., 2007). The process of dehydration occurs in a bath of acetone at a temperature of -25°C to help prevent shrinkage of the specimen. The specimens are placed in 90-100% acetone baths, with a specimen to acetone volume ratio of 10:1. After 7 days, the acetone purity is checked, and the specimens are transferred to a new aliquot of pure acetone. This process continues until the acetone concentration in the bath remains at a level higher than 99%, showing that water has been nearly all replaced by acetone in the specimen (DeJong et al., 2007).

The specimen will proceed to undergo a process known as Defatting or

Degreasing. During this step, the specimen is brought to room temperature while still in the acetone bath of at least 98.5% (Sora et al., 2007). As the fat or lipids of the specimens are removed, the acetone baths will turn yellow in color. The specimen is then transferred to another acetone bath. This step is repeated until the desired level of fat removal is reached. Typically, this is where the most acetone exposure occurs. It is necessary to keep the vats of acetone closed and sealed with a lid to help prevent evaporation of acetone and to limit the amount of acetone vapors in the air. Keeping the lids on is a form of exposure control.

The third step is the forced replacement of the acetone with a curable polymer.

This is possible by applying a vacuum to the process. The specimens are submerged in the liquid polymer which is located in a vacuum tight freezer set at -25°C to -15°C. The vacuum causes the acetone to vaporize/boil, exit the specimen, and leave the container through the vacuum pump exhaust (DeJong et al., 2007). The void of acetone causes the polymer to be drawn into the cells. After a period of 3-5 weeks of pressure adjustments, the specimen should be completely void of acetone and saturated with the curable polymer. The specimens will then undergo a process of curing that will harden the specimen and ultimately create a finished product.

2.2 Acetone

Acetone is an organic solvent found naturally in the environment and it is commonly used during many industrial processes. Humans have low levels of acetone in their bodies that naturally help in the breakdown of fats (U.S. Department of Health and

Human Services, 1994). The process of plastination uses acetone for dehydration and defatting of a specimen.

2.2.1 Properties of Acetone

Acetone is a colorless liquid that produces a fragrant, mint-like odor that is extremely volatile (U.S. Department of Health and Human Services, 1994). It is miscible with water, ethanol, ether, and a variety of other organic solvents, making it a commonly used solvent. The odor threshold of acetone for humans ranges from 100 to 140 ppm

(U.S. Department of Health and Human Services, 1994).

2.2.2 Temperature and Volatility

Organic solvents that are liquid at room temperature pose a significant risk for exposure (Plog et al., 1996). The vapor pressure of acetone is directly related to room temperature. The vapor pressure of acetone at 20°C is 180.0 mmHg. For a lower exposure risk, experiments should be carried out at lower temperatures to reduce vapor generation.

2.3 Exposure Guidelines

The American Conference of Governmental Industrial Hygienists (ACGIH),

Occupational Safety and Health Administration (OSHA), and the National Institute for

Occupational Safety and Health (NIOSH) have set guidelines for occupational exposures to chemicals, noises, and a variety of other risks. Airborne concentrations of certain chemical substances under which it is believed that nearly all workers may be continuously exposed, each day, over an entire working lifetime without adversarial

8 health effects, is known as a Threshold Limit Value (TLV) (Industrial Ventilation, 2013).

OSHA sets a Permissible Exposure Limit (PEL) standard that is enforceable by law.

These limits are based on an 8-hour TWA and also measure the concentration of a substance in the air.

OSHA adopted a Permissible Exposure Limit Time-Weighted Average (PEL-

TWA) for acetone of 1000 ppm. ACGIH has established a Threshold Limit Value Time-

Weighted Average (TLV-TWA) of 500 ppm of acetone. They have also established a

Threshold Limit Value-Short Term Exposure Limit (TLV-STEL) of 750 ppm of Acetone.

NIOSH has established 250 ppm of Acetone as a Recommended Exposure Limit (REL).

The Immediately Dangerous to Life and Health (IDLH) is based on the Lower Explosive

Limit (LEL) to acetone. Because of health considerations in humans, an appropriate value of 5,000 ppm would suffice; however, because of safety considerations, the IDLH is set at 2,500 ppm as that is the LEL for acetone which is mentioned in section 2.4 (Acetone:

Documentation, 1994).

2.4 Flammable Liquids, Flash Points, Explosive Range

The National Fire Protection Association (NFPA) classifies liquids into different divisions based on their flammability. Acetone is considered a Class IB liquid, meaning it has a flash point below 22.8°C and a boiling point above 37.8°C. The lowest temperature a liquid gives off enough vapor to form an ignitable mixture with the air is deemed its flash point. The flash point of acetone is -18.0°C.

Flammable substances have an explosive range, which is a determined concentration of a vapor in air between the lower explosive limit (LEL) and the upper

9 explosive limit (UEL). By definition, the lower explosive limit is, “The lower limit of flammability of a gas or vapor at ordinary ambient temperatures expressed by a percentage of the gas or vapor in air by volume” (Plog et al., 1996). If concentrations are lower than the LEL, a spark or flame will not ignite the vapors in the air because there are not enough particles to withstand combustion (Popendorf, 2006). The particles may also be too spread out within the space to ignite. OSHA prohibits entry into a confined space if flammable or combustible gas or vapor concentrations exceed 10% of the LEL

(Popendorf, 2006). Acetone has a lower explosive limit of 2.5% (10 % of LEL, 2500 ppm). The LEL is indirectly proportional to temperature, thus the LEL will decrease as the temperature of the vapor increases. Acetone will lower its LEL from 2.5% at 25°C to

1.3% at 260°C (Popendorf, 2006).

The upper explosive limit is, “The highest concentration (expressed as the percentage of vapor or gas in the air by volume) of a substance that will burn or explode when an ignition source is present” (Plog et al., 1996). At this concentration, there is not enough oxygen in the air to sustain combustion. Acetone has a UEL of 12.8%. Because of the high amount of acetone use and risk of explosion, the laboratory should be intrinsically safe. An intrinsically safe laboratory means that any electronic circuit located in the lab will not cause any sparking or arcing, eliminating its ability to ignite a flammable vapor.

2.5 Health Effects of Acetone Exposure

Acetone has a wide range of irritant effects that are dependent on the individual being exposed. It is introduced into the body most commonly through inhalation, but also

10 through ingestion and dermal exposure. Because individuals have different responses to acetone vapors, it is difficult to determine a standard occupational exposure limit.

According to Arts, (2002) “...studies reveal large differences in the lowest acetone exposure concentration found to be an irritant to the respiratory tract and eyes, ranging from about 250 to 186,000 ppm.” This is a massive range deemed irritable by people exposed to acetone vapors. Acetone has also been shown to depress the central nervous system (TLVs and BEIs, 2014).

2.5.1 Short-Term Exposure

Inhalation of acetone is rapidly absorbed in the respiratory tract of humans. It is uniformly disseminated throughout the body’s non-adipose tissues where it begins the process of being cleared from the body via liver metabolism and excretion (Arts et al.

2002). Acetone is relatively low on the toxicity scale as compared to similar industrial solvents. Short-term exposures typically cause mild eye and respiratory tract irritation.

This slight irritation typically is reported at concentration levels starting around 250 ppm upwards to 1000 ppm (Arts et al. 2002). When dealing with concentrations as low as 250 ppm, slight alteration in individual parameters on standardized neurobehavioral tests have been shown (AEGLs, 2005). According to Dick (1989), postural sway was also affected when low exposures (250 ppm for four hours) to acetone were tested. He also showed that short-term exposure to acetone increased the time it took for an individual to respond to a noise test, and also increased the rate at which individual’s detected alarms sounds that were not present during an auditory tone task (Dick et. al., 1989). Mood swings and nausea are both acute symptoms of short-term exposure.

Short-term exposures at high concentrations have indicated more severe effects such as vomiting and unconsciousness. These symptoms were demonstrated by individuals who were exposed to acetone concentrations that exceeded 12,000 ppm for a time period of around 240 minutes (AEGLs, 2005). An example of a severe case occurred when two female workers suffered CNS depression along with a loss of consciousness while working in a raincoat manufacturing plant where acetone was the major solvent used (AEGLs, 2005).

2.5.2 Long-Term Exposure

Few studies have shown the effects of long-term exposure to acetone because of its quick excretion from the body. For workers who were exposed to 1,000 ppm of acetone for 3 hours a day from 7 to 15 years had complaints of respiratory tract irritation, dizziness, and loss of strength (Acetone, 2005). In a study on rats, a 19,000 ppm exposure for 8 weeks showed a reversible decrease in absolute brain weight (Arts et al., 2002).

Other experiments have shown that occupational exposure to acetone reduces perceived odor intensity by 800 ppm (Dalton et al. 1997). This could lead to over-exposure situations in which those who are constantly exposed to acetone, become tolerant and unaware of dangerous situations. Relationships between visual demise, the ability of color vision, and contrast sensitivity are all affected by long-term occupational exposure to organic solvents (Costa et. al., 2012).

2.6 Hazard Evaluation

In order to deem a specific process as hazardous, a variety of different questions must be answered. The main goal is to determine if the concentration of the solvent in the

12 air is above that permitted by various regulating bodies. According to Plog, assessing the degree of risk in the workplace is based on:

“(1) The toxicity of the substance, (2) the concentration in the breathing zone, (3)

the manner of use, (4) the length of time of the exposure, (5) the controls already

in place and their effectiveness, (6) any special susceptibilities on the part of the

employees,” (1996).

2.7 Hazard Control

When an individual is at risk from being exposed to concentrations above OELs to certain organic agents or other hazardous materials, steps need to be taken to reduce the risk. There are three levels of control that should be instituted to make the process less dangerous. The first option to be looked at is process control. Replacing a hazardous chemical with a less toxic or less volatile chemical is the most efficient way of controlling exposure. Because acetone is the best option for use during the plastination process, this is not an effective solution.

With the major route of exposure being inhalation, implementing ventilation systems is an effective engineering control. By developing proper closed systems and local exhaust ventilation, reduction of vapors in the breathing zone is greatly reduced.

Another means of hazard control is the application of intrinsically safe devices.

Being intrinsically safe means an area, typically hazardous, has limited energy available for ignition. This occurs by eliminating internal sparking, and enclosing of equipment that does create sparks, (Carson et al., 2002).

2.8 Ventilation in a Laboratory Setting

Worker protection can be improved by proper ventilation. Ventilation does not only regulate odor, moisture, and heat; but can also eradicate unsafe levels of gases, vapors, and particulates in the laboratory space. Ventilation is a combination of both a supply and an exhaust system. The supply system is used to cool or heat air, and place it within a specific area. The exhaust system is made up of two specific types of exhaust: general exhaust, and local exhaust, (Prudent practices, 2011).

2.8.1 General Exhaust

General exhaust is an exhaust system used for expelling large quantities of air within a space. This air may be tempered and recycled if used for heat control, or may be exhausted to the outside when used for contaminant control (Industrial Ventilation,

1995). The supply system and general exhaust system are typically used in union.

2.8.2 Local Exhaust

Local exhaust systems are created to remove process contaminates by capturing them at the source before contaminating the entire workplace environment. These systems are more efficient as they can be localized to exhaust only contaminated air.

Typically, local exhaust systems encompass four basic parts including the hood, the duct system, the air cleaning device, and the fan (Industrial Ventilation, 1995). The flow rate of the hood is dependent on all four basic parts. In order to capture gases, vapors, and fumes, the local exhaust will need to create a flow pattern that will have enough capture velocity. The capture velocity is defined as “air velocity at any point in front of the hood or at the hood opening necessary to overcome opposing air currents and to capture the

14 contaminated air at that point by causing it to flow into the hood” (Industrial Ventilation,

1995). There are a variety of different hood types that can be chosen based on processes involved.

2.8.2.1 Hoods in Exhaust Systems

One critical feature of Local Exhaust Ventilation (LEV) is the design and use of a hood. A hood is the entry point for which contaminated air is pulled into the exhaust system. Any suction opening is considered a hood and is the point of all air entry into the duct. The hood converts static pressure in the duct into velocity pressure. If a contaminant is not controlled by the hood, the local exhaust system has failed (Plog et al., 1996). “The more completely the source of contamination is enclosed, the more positive the control, and the lower both the exhaust volume and cost of the exhaust system,” (Alden et al.,

1982). Capture hoods are designed to sufficiently collect all contaminants and draw them into the exhaust system. To do this, the capture velocity must be at a high enough level.

The capture velocity is defined as, “Air velocity at any point in front of the hood or at the hood opening necessary to overcome opposing air currents and to capture the contaminated air at the point by causing it to flow into the hood,” (Plog et al., 1996).

2.8.2.2 Hood Design

According to Plog (1996), there are six principles of designing an efficient hood,

“(1) Enclose the operation as much as possible to reduce the rate of airflow needed to control the contaminant, and to prevent cross drafts from blowing the contaminant away from the field of influence of the hood; (2) Locate the hood so that the contaminant is moved away from the breathing zone of the operator; (3) Locate and shape the hood so

15 that the initial velocity of the contaminant will throw it into the hood opening; (4) Solvent vapors in health-hazard concentrations are not appreciably heavier than air. Capture them at their source rather than attempt to collect them at the floor level; (5) Locate the hood as close as possible to the source of the contaminant; (6) Design the hood so that it will not interfere with the worker.”

There are a variety of different types of hoods. These include; 1) local hoods 2) side downdraft, overhead hoods 3) booths or enclosures (Alden et al., 1982). Local hoods are relatively small and enclose or are located near a source of contamination.

They are designed to capture the contamination before dispersion has the ability to occur.

Side downdraft or overhead hoods are generally a larger concept of local exhaust hoods.

They rely on a larger volume of exhaust. The third design known as booths or enclosures is the most effective design as they isolate contamination generation from the rest of the workspace. These are often large and expensive to construct.

The rules of designing an exhaust hood are summed up in five general guidelines according to Alden in Design of Industrial Ventilation Systems;

1. Reduce the cause of dispersion as far as possible by modification of the

process, machine or material before designing hoods.

2. Place the hood as close as possible to the source of contamination

preferably enclosing it.

3. Locate and shape the hood so that the contaminant released from the

source is either directed into the mouth of the pipe.

4. Cause air to flow past the dust source and into the hood with a velocity

at the point of dust origin greater than the velocity of escape of the

particles.

5. So locate the hood that the operator is never between the dust source

and the hood.

Factors needed to be considered include cross drafts, hood size, duration of contaminant generation, and overall toxicity of chemical agent (Flynn, 2002)

2.9 Administrative Controls

Administrative controls are designed to reduce employee exposure by reducing work time in areas of high exposure. Administrative controls also include training for individual workers on hazard recognition and certain work practices that apply to their specific work activities. This can be accomplished by altering work schedules to reduce time spent in the area. By adding additional workers, time of exposure can be reduced.

Also, the proper training is required and can help in any control effort.

2.10 Personal Protective Equipment

One of the most common forms of personal protective equipment (PPE) to reduce inhalation exposure is a respirator. Respirators should be used as the last line of defense, and should not be the primary solution to an over-exposure situation. OSHA states this in

29 CFR,

“1910.134(a)(1) In the control of those occupational diseases caused by breathing

air contaminated with harmful dusts, fogs, fumes, mists, gases, smokes, sprays, or

vapors, the primary objective shall be to prevent atmospheric contamination. This

shall be accomplished as far as feasible by accepted engineering control measures

(for example, enclosure or confinement of the operation, general and local

ventilation, and substitution of less toxic materials). When effective engineering

controls are not feasible, or while they are being instituted, appropriate respirators

shall be used pursuant to this section.”

Respirators require an extensive amount of care and maintenance to remain effective and can often be used incorrectly. If not properly fitted, the mask can leak.

Respirator use typically requires a medical clearance and can also put a strain on the respiratory systems of individuals who use them (Plog et al., 1996). Specific cartridges are obligatory for the exact chemical vapor of concern. Another concern with respirators is that they will not control the LEL. Because of the inherent chance for human error, the first two options of hazard control are recommended (Plog et al., 1996).

Due to the risk of dermal exposure to acetone, gloves are required during the specimen transfer. Because of the solvent permeation rates associated with acetone, an underlying pair of nitrile gloves, covered by a pair of rubber gloves is required in the plastination lab. The amount time it takes for a chemical to infiltrate a glove is based on the thickness and composition of the glove, (Plog et al., 1996).

2.11 Summary

Research has shown and proven that organic solvents pose health risks to those who are exposed to them in high concentrations. It is rational to foresee that exposure to acetone above permissible limits is occurring during the plastination process when

18 ineffective ventilation systems are the primary means of hazard control. It is presumed that the highest levels of exposure during the plastination process will arise when specimens are transferred to and from vats of >90% acetone is occurring. If levels of acetone exposure exceed the permissible exposure limits, health effects will arise, as proven by numerous research studies. Flammability of acetone is also of great concern.

Lower explosive limits and upper explosive limits should be taken into consideration when designing a laboratory that produces large amounts of acetone vapors. The ability to expel high levels of vapors from a laboratory may be accomplished by designing a specialized exhaust system for the space. Implementing hazard control guidelines for acetone exposure prevention in a plastination laboratory will help occupational health professionals gain knowledge in providing a safe plastination laboratory setting.

Chapter 3

Materials and Methods:

3.1 Overview An industrial hygiene air sampling investigation was conducted in a plastination laboratory previously shown to have high levels of acetone vapor concentrations. In total, four separate local exhaust systems were evaluated during the specimen transfer throughout the acetone treatment cycle. Exposure sampling was collected using the following:

MiniRAE 2000 Portable VOC Monitor PGM-7600 Serial Number: 014202

Exposure concentrations were logged during the entire specimen transfer process; typically 10 to 60 minutes. The STEL, TWA, and AVG value of exposure to acetone were calculated by the MiniRAE 2000 computer software known as ProRAE-Suite. Data was combined and placed into a spread sheet. Comparisons of all four ventilation designs

20 were used to determine which system provides the most effective means of control through comparison of descriptive statistics.

3.2 Location

Acetone exposure sampling was conducted within an existing university laboratory dedicated to the plastination process. The laboratory is located in Ohio and has recently been redesigned to house the plastination laboratory. Appendix A contains the layout of the laboratory along with square footage and room dimensions. The laboratory has a total volume of 4450 cubic feet. There are two doors that enter this room. Within this laboratory, there are a total of four acetone filled vats, each containing on average 25 gallons of acetone. Three vacuum freezers are also located on the south wall of the room, used in the final process of polymer impregnation. On the east wall, a specimen washing tub is located. This tub has a continuous replacement of water that aids in the rinsing of specimens of residual formalin solution. This first room, 1400G, is where the first three samplings occurred.

After data analysis revealed the different ventilation systems tested at location

1400G were ineffective at removing the vapors below occupational exposure limits and the LEL, the process was relocated into room 1400B which has a slotted hood (with a dedicated exhaust fan) located on one wall, and supply air on the opposite wall. The room is 680 cubic feet and has one entry point. The room is designed as an intrinsically safe space with grounding bars located on two of the four walls. Dimensions of the slotted hood are shown in Appendix G.

3.3 Initial Lab Ventilation Room 1400G

The initial ventilation of the room was strictly general exhaust. No local exhaust was used in this specific area. Appendix A contains the location of supply and exhaust ducts in the room. There are two ceiling supply vents, and one vent located near the floor.

The laboratory has one ceiling exhaust vent and two floor exhausts as shown in Figure A-

3 in Appendix A. The size of the vents on the supply ceiling ducts are each 12 inches by

13 inches. The floor supply vent measures 12 inches by 10 inches. The exhaust vent on the ceiling measures 12 inches by 8 inches, with floor vent sizes of 12 inches by 10 inches. A previous sampling of air changes per hour was carried out by a university employee who specializes in HVAC systems. Measurements demonstrated the laboratory at 6.69 air changes per hour and the room was positive to the surrounding rooms.

3.4 Sampling Areas and Times

The laboratory technician who is directly involved in transfer of specimens from one acetone vat into another was sampled for the amount of time it takes to complete the task (typically 10-60 minutes). The technician was sampled in the plastination laboratories pictured in Appendix A. An initial study was carried out to determine acetone exposure concentrations in room 1400G with the provided dilution ventilation system on 11/26/12. The initial study indicated high levels of exposure and levels near the LEL. Alterations were made in the laboratory general ventilation system by increasing air changes per hour and negativity of the area compared to surrounding spaces and a follow up sampling study was completed on 12/21/12. A third sampling occurred after installation of a slotted hood into the general exhaust ventilation system on

10/18/13. The four acetone baths were relocated to room 1400B on 3/8/14. A fourth and final sampling occurred in room 1400 B, which contains a slotted hood with dedicated exhaust system, occurred on 3/10/14. During all four samplings it was determined if the acetone vapors were reaching lower explosive limits.

3.5 Equipment and Supplies

Sampling was conducted using a calibrated MiniRAE 2000. This instrument is a handheld volatile organic compound (VOC) detector with a photoionization detector

(PID) that ranges from 0 to 10,000 ppm. A PID samples vapors in air by passing organic vapors by a UV lamp, photo-ionizing them, and detecting the ejected electrons. The

MiniRAE 2000 uses a 10.6eV lamp.

It contains an integrated sampling pump that delivers a 450 to 550 cc per minute flow rate (MiniRAE 2000 User’s Guide). Figure 3-1 pictured below, shows the MiniRae that will be used in this study. This instrument is ideal as its ability to overcome high humidity locations and produce an accurate reading due to the design of its humidity and temperature sensors. Sampling equipment includes the MiniRAE 2000, 6-inch tygon tubing, Zero Air calibration gas, and an isobutylene calibration gas/kit.

Figure 3-1 MiniRae 2000

Photoionization detectors operate by pulling an air sample and exposing it to a pre-determined wavelength. The resultant ions that are generated are collected and the current is converted electronically into a signal that is displayed to the user in a digital format, (Plog et al., 1996).

3.6 Sampling Procedures and Data Collection

3.6.1 Pre-Calibration of MiniRae 2000

The MiniRAE 2000 was fully charged for a minimum of 6 hours, which was indicated by the docking cradle showing a continuous green light, and the message of

“Fully Charged” being displayed on the instrument. The instrument was factory calibrated with a standard calibration gas. It was calibrated with isobutylene which has a calibration span of 100 ppm. The acetone correction factor was applied to accurately

24 measure acetone vapor exposure. This instrument was set to acetone readings by selecting the gas in the library of the instrument shown below in Table 3.1, displaying the built in correction factors for acetone along with the pre-set PID span and alarm settings.

After this, the instrument was zero air calibrated using fresh air. Calibration occurred at a temperature similar to that of the laboratory where sampling occurred.

Table 3.1: MiniRAE 2000 Acetone Correction Factor and Alarm Settings

MiniRAE 2000 Correction Factor Pre-set PID Span and Alarm Settings Compound 10.6 eV Span High Low TWA STEL Acetone 1.1 100 500 250 500 750

3.6.2 Sampling and Data Collection

Sampling occurred within the breathing zone of the personnel carrying out the specimen transfer. All doors in the laboratory were closed during the process. The

MiniRAE 2000 was used to measure the total VOC within the breathing zone of lab personnel. Time of logged samples occurred every 60 seconds and sampling continued for the total time needed to complete the task (10-40 minutes). The following procedure was adhered to when collecting data during all four samplings:

1. The PID was turned on and pre-set to acetone.

2. The PID was calibrated prior to use.

3. The PID was zeroed using fresh air before entry into the laboratory.

4. Sampling began upon entry into the laboratory by holding the PID at a

breathing level of laboratory personnel while not interfering with process.

5. Sampling ran during the duration of the process.

6. Upon exiting the laboratory, the PID was stopped.

3.6.3 Post-Sampling Data Collection

Data collected was uploaded to a computer using the software designed by

MiniRAE 2000 known as ProRAE-Suite. Data collected indicated following:

1. Data points collected

2. Calibration date and time

3. Sample period

4. High and low alarm levels

5. Max number of vapor present in ppm per sampling point

6. Average number of vapor present in ppm per sampling point

7. The STEL, TWA, or AVG value of specific events will determined in this

software

8. Logged data in graph mode

Chapter 4

Results

4.1 Overview After initial evaluation of the existing dilution ventilation system in 1400G indicated high levels of acetone exposure, and peaks hitting above the LEL, an increase in air changes per hour and overall negativity of the lab was increased. After little change, an exhaust hood was relocated to the plastination lab and ducted to the dilution ventilation system to be used as local exhaust. Sampling occurred in the plastination lab showing results with little improvement. A final decision of moving the plastination process to a new room with a slotted hood and a dedicated exhaust fan was the result.

4.2 Dilution Ventilation in Room 1400G

Comprehensive data sets of VOC concentrations are presented in Appendix B.

This data was collected in an investigatory attempt at determining a baseline of exposure to acetone in the plastination lab. No adjustments had been made to the original laboratory general ventilation at this point. Table 4.1 provides a summary of acetone monitoring data using the MiniRAE 2000 (PMG7600) carried out on 11/26/12.

Table 4.1: Dilution Ventilation in Room 1400G 11/26/12 Results

The monitoring conducted on 11/26/2012 indicated personal exposure to acetone below the 8 hour TLV-TWA with 47.9 ppm. However, sampling showed a 15-min STEL of 1409.1 ppm ascertaining exposure above the 15-min STEL according to ACGIH guidelines. Appendix B shows points exceeding the LEL guidelines towards the end of the process.

4.3 Adjusted Dilution Ventilation in Room 1400G

Re-sampling was conducted on 12/21/12 after facilities maintenance a for this location by increasing fan speed to ultimately make the laboratory more negative as compared to surrounding areas. Originally the room was at 6.69 air changes per hour and the room was positive to the surrounding rooms. The room was adjusted to be at 4.93 air changes per hour to the negative. In order to determine these readings, the employee used a Vane Anemometer. With an increase in exhaust, the monitoring conducted on

12/21/2012 decreased concentrations but continues to indicate personal exposure to acetone above the 15-minute TLV-STEL as shown below in Table 4.2. A comprehensive set of data points for this sampling period can be found in Appendix C.

Table 4.2: Adjusted Dilution Ventilation in Room 1400G 12/21/12 Results

Sample 8-hr 15-min 8-hr 8-hr 8-hr 15-min. Time TWA STEL Name of TWA TWA TWA STEL (min) (PPM) (PPM) Personnel Date (PPM) (PPM) (PPM) (PPM)

or Area OSHA NIOSH ACGIH ACGIH PEL REL TLV STEL Technician #1, FSB 12/21/12 10 28.5 912.4 1000 250 500 750 1400G

Since exposure exceeded the 15-minute STEL, the lab technician was medically cleared and fit tested for a full face respirator for use during the plastination process until engineering controls could be altered. Although respiratory protection decreases the external exposure concentrations to acetone, there is a concern about peak levels exceeding the 10% of the lower explosive limit.

4.4 Local Exhaust Ventilation Slotted Hood #1 in Room 1400G

A slotted hood was located and installed in the plastination laboratory above the acetone vats. The slotted hood was primarily developed for a laboratory that molded cast iron parts used to reflect radiation treatments. Due to monetary restrictions in creating a new hood for the plastination lab, this was the best option. It was linked into the current exhaust duct in the room by adding 6” round galvanized duct work. Below is a picture of the exhaust hood installed above the acetone baths in room 1400G.

Figure 4-1: Slotted Hood #1 in Room 1400G

Monitoring was conducted using the MiniRae 2000 PID by holding the instrument in the breathing zone of the individual performing the plastination procedure.

The monitoring conducted on 10/18/13 indicated personal exposure to acetone below the

8-hour TLV-TWA, above the 15-minute STEL, and produced several readings above the

LEL. Table 4.3 indicates a summary of the results collected on 10/18/13. Appendix D displays the comprehensive set of data point obtained during this monitoring.

Table 4.3: Local Exhaust Ventilation Slotted Hood #1 in Room 1400G 10/18/13 Results

4.5 Local Exhaust Ventilation Slotted Hood #2 in Room 1400B

Due to levels peaking above the LEL and exposure above the 15-minute STEL, the process was relocated to room 1400B. This room was originally designed with a slotted hood for management of volatile hazardous waste. It contains a slotted fume hood, connected to its own exhaust fan. There is also a supply air fan dedicated to the room for the provision of make-air within the space. Below shows the slotted hood and layout of the new location.

Figure 4-2: Slotted Hood #2 in Room 1400B

Monitoring was conducted using the MiniRae 2000 PID by holding the instrument in the breathing zone of the individual performing the plastination procedure.

The monitoring conducted on 3/10/14 indicated personal exposure to acetone below the

8-hour TLV-TWA, below the 15-minute STEL, and produced only the first 3 readings above the LEL (due to initial opening of vats). Table 4.4 indicates a summary of the results collected on 3/10/14. Appendix E displays the comprehensive set of data points obtained during this monitoring. The 15-minute STEL was calculated excluding the initial three readings. This was concluded because the readings occur upon initially opening the vats of acetone, and does not give time for the hood to clear the room.

Table 4.4: Local Exhaust Ventilation Slotted Hood #2 in Room 1400B 3/10/14

Results

Chapter 5

Discussion

5.1 Overview After sampling four different ventilation systems, the local ventilation system with a dedicated supply and exhaust fan proved to be the most effective design for removing acetone vapors during the plastination process. Upon reviewing the data, it was demonstrated that after each change, improvement had been made regarding the areas of concern (15-minute STEL, Lower Explosive Limit). Because the process normally does not last longer than 1 hour, the 8-hour TWA was not an issue when calculated. However, the data revealed the 15-minute STEL as exceeding the allowance set forth by ACGIH in the initial three samplings. A comparison of the results shows dramatic fluctuation in the

15-minute STEL based on which ventilation system was utilized. The final adjustment of relocating the process into the room 1400B with a dedicated exhaust, separate supply fan and a slotted hood was the only change that resulted in levels below the 15-minute STEL limit of 750 ppm. This is shown in the summary table 5.1.

Table 5.1: Summary of Lab Data and Calculated Time Weighted Averages for

Acetone

Sample 8-hr 15-min 8-hr 8-hr 8-hr 15-min Name of Time TWA STEL TWA TWA TWA STEL Personnel Date (min) (PPM) (PPM) (PPM) (PPM) (PPM) (PPM) or Area OSHA NIOSH ACGIH ACGIH PEL REL TLV STEL Technician #1, 11/26/2012 20 47.9 1409.1 1000 250 500 750 FSB1400G Technician #1, FSB 12/21/2012 10 28.5 912.4 1000 250 500 750 1400G Technician #1, 10/18/2013 61 45.4 877.8 1000 250 500 750 FSB1400G Technician #1, 3/10/2014 18 31.9 517.2 1000 250 500 750 FSB1400B

As shown, the 15-minute STEL started at 1409.1 ppm with only general exhaust as the primary method of removing acetone vapors from the space. By negativity of this location, the 15-minute STEL was reduced to 912.4 ppm, but was still over the ACGIH’s limit of 750 ppm.

The next step in the process was to add local ventilation. The process involved installing a previously used slotted hood above the acetone vats in room 1400G. The hood was installed by merging it into the already established general exhaust of the room.

Because of monetary issues, the hood was poorly installed with many different elbows and transitions, and did not have a dedicated exhaust fan. The existing fan was required

34 to overcome friction loss due to the capture system and its duct work to produce the required flow rate. The current exhaust fan was unable to pull enough air to create a face velocity of over 100 fpm, or capture efficiency at the slotted hood, and showed no real improvement in capturing the acetone vapors from the room. The 15-minute STEL was still above ACGIH’s guidelines at 877.8 ppm. Results also showed multiple readings exceeding the lower explosive limit.

The process of defatting using acetone was relocated to room 1400B. This room had been previously used as volatile waste bulking facility. It is designed as an intrinsically safe room, and has a slotted hood and supply make-up air system each with their own dedicated fans. This is different than the original hood #1 in room 1400G, which was connected to the general dilution ventilation system already present in the lab.

The resulting changes proved to be successful as it reduced the 15-minute STEL to 517.2 ppm. This recording is 232.8 ppm below the ACGIH 15-minute STEL for acetone, and is

891.9 ppm below the original 15-minute STEL collected in October of 2012.

The final slotted hood system demonstrated levels over the lower explosive limit.

These points were collected the first three minutes the acetone vats were opened. These results are suggested to be due to the initial burst of acetone vapors from opening the closed vats. The previous locations showed the LEL to be breached at times closer to the end of the process. The build-up of acetone vapor was occurring as the process proceeded, because the inability of the exhaust systems to clear acetone vapors from the room. In the final room, 1400B, the slotted hood #2 proved to be more effective. The initial burst above the LEL is likely due to opening of the vats in a smaller location. This initial excursion above the LEL is acceptable based on the fact that the room is

35 intrinsically safe and is offset by the benefits in decreased occupational exposures to personnel. The room 1400B is only 680 square feet, as opposed to 4450 square feet of the lab 1400G. According to Ukai (2004), the vapor concentration in a small scaled solvent workplace is up to three times higher than a large scale enterprise. The sampling results showed that as time passed in room 1400B, the initially high level of acetone vapors decreased. This proves that the ventilation system was working properly, and the initial high blip above the LEL was due to overloading the room with acetone vapors upon opening the vats. Vapor concentrations will always remain high within the head space of the acetone vats due to acetone’s vapor pressure. The acetone vats have to remain closed to prevent loss of product and is a desirable control to prevent inadvertent release of acetone vapor while technicians are within the space.

5.2 Limitations

Many limitations exist when sampling for acetone vapors during the plastination process. As with all vapors, temperature can change the chemicals volatility. To help reduce this variability, temperature in the labs were kept consistent between 15-21°C. As discussed in the Literature Review, the vapor pressure of acetone at 20°C is 180.0 mmHg, thus to lower exposure risks, experiments should be carried out at lower temperatures to reduce vapor generation.

Sampling time is also a limiting factor. The process of transferring specimens from vats of acetone can range from 10 minutes up to 60 minutes depending on the amount of specimens and their overall size. Sampling times varied in the data collection

36 because the amount of specimens varied and based on their size. It was determined that sampling the entire process would represent the actual exposure most accurately.

5.3 Recommendations for Future Studies

Recommendations for future studies include:

 Processes vary from day to day depending on size of specimen, duration,

and amount of fat, temperature, etc. Repeat this study using a process that

releases a set amount of vapors to determine more accurate comparisons

between the different exhaust systems.

 Design a flanged slotted hood and determine if design is more effective

than previously sampled designs.

5.4 Conclusions

The following hypotheses were tested and failed to be rejected:

 The measurement of airborne acetone concentration in the breathing zone

of workers will not exceed the OSHA PEL of 1000 ppm during the

plastination process.

 The measurement of airborne concentration of acetone in the general area

within the procedural rooms will be above the Lower Explosive Limit

(LEL).

 The installation of a local exhaust ventilation system will decrease the

measured level of acetone in the breathing zone of workers.

 The installation of a local exhaust ventilation system will lower the

concentration of acetone below the Lower Explosive Limit (LEL).

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Appendix A.

LABORATORY LAYOUTS

A-1: Laboratory 1400G Layout and Square Footage

A-2: Initial Laboratory 1400G Arrangement

A-3: Pre-Alteration Ventilation in Laboratory 1400G

A-4: Laboratory 1400B Layout and Square Footage

Appendix B.

Dilution Ventilation in Room 1400G 11/26/12 Results

Appendix C.

Adjusted Dilution Ventilation in Room 1400G 12/21/12 Results

APPENDIX D.

Local Exhaust Ventilation Slotted Hood #1 in Room 1400G 10/18/13 Results

Appendix E.

Local Exhaust Ventilation Slotted Hood #2 in Room 1400B 3/10/14 Results

Appendix F.

F-1: Slotted Hood #1 Picture and Measurements

Appendix G.

G-1: Slotted Hood #2 Picture and Measurements