Firefighter Safety Depends on Gas Detector Accuracy by BRUCE LAKE

Continuing Education Course

Firefighter Safety Depends on Gas Detector Accuracy BY BRUCE LAKE

TRAINING THE FIRE SERVICE FOR 135 YEARS

To earn continuing education credits, you must successfully complete the course examination. The cost for this CE exam is $25.00. For group rates, call (973) 251-5055. Firefighter Safety Depends on Gas Detector Accuracy

Educational Objectives On completion of this course, students will

1) Review a case study involving complacency towards equip- 3) Review the importance of calibration. ment maintenance. 4) Determine several causes of “False Positives” while 2) Discover common types of monitoring and detection equip- monitoring atmospheres. ment carried by fire apparatus.

BY BRUCE LAKE sensor; or the multisensor gas monitor, usually equipped with

lower explosive limit (LEL), oxygen (O2), CO, and hydrogen

irefighters are not perfect. They have short- sulfide (H2S) sensors. The LEL sensor detects flammable gases,

comings just like other mortals. Some common sins the O2 sensor detects oxygen enrichment or deficiency, and include complacency toward mainte- the CO and H S sensors detect toxic gases. F 2 nance and the “we’ll figure it out on scene” 1 Regardless of the brand or model that your mentality. Together, these two liabilities can fire department uses, the technology found produce disastrous results. On May 7, 2009, inside all of these popular devices is basical- eight firefighters were injured as a result of a ly the same. Catalytic bead or electrochemi- natural gas explosion inside a Maryland strip cal sensor technology converts the presence mall. The National Institute for Occupational of flammable or toxic gas into an electrically Safety and Health (NIOSH) investigation measurable signal, which is usually dis- report recommended that “fire departments played as a number. Teams with strong fun- should ensure gas monitoring equipment damentals tend to be more successful than is adequately maintained and firefighters others. The fundamentals of gas detection are routinely trained on proper use.” Fire involve consistent maintenance and accurate departments can reduce the odds of repeating interpretation of the numbers. similar incidents by maximizing the accuracy Poorly maintained gas monitors will pro- of their gas detection equipment and by train- duce inaccurate readings, which may con- ing personnel how to accurately interpret gas tribute to bad decisions affecting civilians readings. and firefighters, such as unnecessary Today, first-due apparatus often 2 evacuation or exposure to a danger- carry monitoring and detection equip- ous atmosphere. Firefighters can easily ment. Modern technology has reduced ensure accurate readings by calibrating the size, cost, and complexity of gas the gas monitor and by avoiding activi- monitoring devices. First-due compa- ties that harm gas sensors. nies are commonly equipped with one of two popular gas detection devices: CALIBRATION the single-sensor gas monitor, usually Gas sensors start losing accuracy equipped with a carbon monoxide (CO) soon after they are manufactured as a normal result of exposure to air and other gases. The loss of accuracy is called “sensor drift.” Older sensors and (1) Photos by author. those that have been exposed to high www.FireEngineeringUniversity.com Gas Detector accuracy ●

3 4 5

concentrations of their target gas (the and corrode sensors (photo 2). Manu- 6 gas that the sensor is designed to detect) facturers generally provide a two-year have greater sensor drift. sensor warranty. The O2 sensor tends to Calibration is one way to compensate have the shortest lifespan because it is for sensor drift. During the calibration, a constantly exposed to oxygen. CO and sensor is exposed to a specific concentra- H2S sensors usually last longer than two tion of target gas. Because of sensor drift, years. The LEL sensor lifespan will vary the amount of gas the sensor detects will based on its exposure to high concentra- differ from the amount of target gas to tions of flammable gases or poisons. LEL which the sensor was actually exposed. sensor poisons include silicone vapors Calibration determines the difference and (found in caulking, moisture-removing adjusts the instrument readings up or lubricants, and some vehicle appearance down to compensate. Regular calibration care products), leaded gasoline vapors, is necessary to ensure accurate readings. diesel exhaust, and refrigerant gases (fre- Most manufacturers recommend that their ons). Simple preventive measures such as gas sensors be calibrated monthly and af- storing the device in an interior compart- ter a significant gas exposure. Check your ment, not an exterior one (exposure to operations manual for the recommended cold reduces battery life), and not allow- calibration schedule. ing the device to get immersed or even The span reserve of a gas sensor is the soaking wet (water is bad for electron- amount of life remaining in it; sensors ics) can avoid on-scene frustration. The with less than 50 percent of their span reserve remaining will only way to ensure that your gas monitor and the numbers it fail calibration and must be replaced. Sensor span reserve displays are accurate is through regular calibration and daily values can only be determined through calibration. The values inspection. are displayed on the monitor at the end of each sensor’s There is more to using a gas monitor than knowing how to calibration and are recorded in the instrument’s calibration turn it on and off. Firefighters need confidence in their ability records. to accurately interpret what the gas monitor is telling them. Using expired calibration gas may also cause inaccurate This confidence is developed through training and experience. meter readings. Calibration gas will naturally degrade over time; shelf life varies from months to years, depending on the LAG TIME gas mixture. When a bottle of calibration gas has exceeded its Gas monitors do not provide instantaneous results. It takes expiration date, the specific concentration of gas needed for between 20 seconds and two minutes for a gas sensor to calibration no longer exists (photo 1). process a sample of gas and display a number, which is called the “lag time.” If you are walking nonstop from room to room HARMFUL SUBSTANCES noting gas readings, any numbers the monitor produces will Exposure to harmful substances can destroy sensors or at not accurately reflect the gas concentrations in your current least reduce their accuracy. For example, holding a gas moni- location. If you are using tubing or an extension probe, the tor next to an idling apparatus exhaust pipe will clog, coat, lag time will be longer, typically an additional two seconds

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Table 1. False Positive Sources

Gases that produce Gases that produce

false CO readings Source false H2S readings Source Hydrogen Recharging batteries Nitrogen dioxide Internal combustion engines, pulp mills Acetylene Welding/soldering Chlorine Water and sewage treatment plants Alcohol-based products Body spray, cooking wine, Sulfur dioxide Combustion of coal home brewing or petroleum Nitrogen dioxide Diesel exhaust Carbon monoxide Incomplete combustion Perchloroethylen Dry cleaning chemical Nitric oxide Metal etching, blasting

per foot of tubing or probe. Check your monitor’s operating be equipped to conduct diffusion sampling. The CO and H2S

manual to confirm the lag time of particular sensors (photo 3). sensors do not require O2 when monitoring. A gas sensor can sense only target gases that are in close proximity to the sensor or directly in front of the inlet port of FALSE POSITIVES attached tubing/probe. Gases can sink, rise, hang around, or Some nontarget gases that are chemically similar to your do any combination of movements depending on their vapor target gas may produce a “false positive” or a sensor reading

density, natural or manmade air currents, temperature, and that is not the result of exposure to a target gas. CO and H2S weather conditions. Using the three-step low/middle/high sensors routinely produce false positives. Some sources of CO

gas sampling technique will improve your chances of finding and H2S false positives are listed in Table 1. target gases. Nontarget gases do not affect the LEL sensor. Humidity First, hold the gas monitor low below your knees for 20 (moisture in the air) and oxygen-displacing gases affect the

seconds. Most gases are heavier than air, which is the reason we O2 sensor and will lower its readings. An O2 reading of 20.9 start low. If during those 20 seconds the numbers start to change, percent by volume is considered normal. wait a full two minutes before reading the number (photo 4). Second, move the monitor to waist height for 20 seconds. EXPOSURE LIMITS If during that 20-second interval the numbers start to change, Exposure to any hazardous material can be considered wait a full two minutes before reading the number (photo 5). safe as long as the exposure is below a specific amount.T he Third, move the monitor above your head for 20 seconds. If authority having jurisdiction (AHJ) will mandate an exposure during those 20 seconds the numbers start to change, wait a standard for your fire department to follow.T he intent of this full two minutes before reading the number (photo 6). standard is to protect firefighters and civilians from exposure Repeat this low/middle/high technique at any entrance to to dangerous concentrations of hazardous materials. The AHJ a structure, room, or point of interest within the investigation standard is usually adapted from the Occupational Safety and area. If more than one gas monitor is available, take advantage Health Administration (OSHA), NIOSH, or the American Con- of this resource. Extra monitors will reduce the amount of ference of Governmental Industrial Hygienists (ACGIH). The time spent hunting for the source of a gas leak. They will also “time weighted average” (TWA) is a term OSHA, NIOSH, and provide redundancy and confirm any unusual readings. the ACGIH use. The OSHA and the ACGIH TWA state that a If any sensor has been exposed to a concentration of gas healthy worker can be safely exposed to a specific amount of beyond its maximum detection limit, the sensor display may a specific hazardous material for eight hours a day, 40 hours read “OR” (over range), “+++” symbols, or “ERR” (error). Check per week with no adverse health effects. The NIOSH TWA is your operations manual to confirm how your sensors will re- based on a weekly exposure rate of 10 hours a day, 40 hours act. Newer LEL sensors will also turn themselves off to prevent a week. deadly exposure to a high concentration of flammable gas. You can use the TWA as a conservative respiratory protection decision-making benchmark. For example, most gas OXYGEN AND LEL sensors have two alarms. Set the first alarm below theT WA

Always check O2 levels when monitoring for flammable to warn firefighters that they must be prepared to evacuate

gases. The LEL sensor requires a specific amount of O2 to civilians and don respiratory protection. Set the second alarm

function properly. If less than the required amount of O2 is at the TWA. At this final alarm, firefighters must ensure that present, the LEL sensor will produce an inaccurate number. all civilians have been evacuated and that all firefighters have Check your operations manual to confirm the minimum donned respiratory protection. The ACGIH TWA for CO is 25

amount of O2 your LEL sensor requires. When less than the parts per million (ppm); for H2S, it is 10 ppm.

minimum amount of O2 is present, a diffusion sampling tech- In addition to respiratory protection requirements, firefight- nique is required so the LEL sensor will produce an accurate ers must also know when conditions are untenable. Many reading. A confined space or hazardous materials team should fire departments use 10 percent of LEL as benchmark for

www.FireEngineeringUniversity.com Gas Detector accuracy ● flammable gas incidents. A reading a toxic, colorless, odorless, and taste- 7 of 0.0 percent of LEL is considered less gas. A product of combustion, safe. A reading between 1.0 and 10 it is commonly found where fuel- percent of LEL is unsafe for civil- burning appliances are malfunction- ians but safe for firefighters wearing ing. Firefighters use positive-pressure respiratory protection and personal ventilation to clear structures of the protective equipment (PPE). Read- products of combustion. A positive- ings greater than 10 percent of LEL pressure fan’s gasoline engine are considered dangerous. Evacuate will increase CO levels inside the everyone until LEL readings are be- building when running outside the low 10 percent. O2 readings between entrance of a building.

19.5 and 23 percent by volume are H2S is a toxic, colorless gas that generally considered safe. Readings smells like rotten eggs and is pro- of less than 19.5 percent by volume duced when organic materials decay. are unsafe for civilians but safe for The most significant sources of H2S firefighters wearing respiratory pro- are petrochemical industries and tection. O2 readings above 23 percent wastewater facilities. Ethyl mercap- by volume are dangerous because tan, an odorant that also smells like the ignition point of all materials has rotten eggs, is added to propane and been lowered. Exit the hazard area natural gas so that people can detect immediately if the LEL or O2 sensors have been compromised leaks by smell. If you can smell rotten eggs, you may not nec- by high concentrations of gas, poisions, or low O2 levels. essarily be dealing with H2S. It’s not practical or possible for a first-due company to Finally, don’t compare your gas detection equipment to detect every gas or vapor that may be encountered. Remem- that of the utility company. The utility company uses different ber, you can’t help anyone if you’re dead, and you can’t enjoy sensors that are more sensitive, designed to detect gas in very retirement if you have cancer. Wear full PPE including respira- minute concentrations. These sensors have higher mainte- tory protection during suspicious odor investigations and nance requirements and are more sensitive to nontarget gases. overhaul.

FLAMMABLE GASES ••• Flammable substances are the most frequently encountered hazardous materials. The LEL sensor in conjunction with the

O2 sensor will be used to size up this invisible threat. As men- When a gas monitor fails to perform as expected, firefight- tioned earlier, many fire departments deploy a single-sensor ers are quick to remark, “That gas monitor is a piece of junk.” gas monitor equipped with a CO sensor. A CO sensor is not The truth is that neglect of routine maintenance and a lack designed to detect any flammable gas or vapor. Don’t use a of knowledge are typically the sources of most gas detection CO sensor to detect propane, natural gas, gasoline or diesel problems. Modern technology has not eliminated the need for vapors, or anything else that will burn. ongoing maintenance and training. Basing decisions on the readings of poorly maintained equipment or on the interpreta- CORROSIVE GASES tions of untrained personnel is a recipe for disaster. ● Corrosive substances are the second most commonly encountered hazardous materials. The standard multisensor package

(LEL, O2, CO, H2S), will not detect corrosive gases. Strong corrosive gases with high vapor pressure will destroy these sensors and burn firefighters through their bunker gear. By simply attaching a small piece of inexpensive universal pH paper to the top of your gas monitor, you can reduce the risk of exposure to corrosive gases. The pH paper turns dark red if a strong acid is present and dark blue if a strong base is present. In either situa- ● tion, withdraw to a safe location and call a hazardous materials BRUCE LAKE is a hazardous materials technician and chemical, biological, radiological, and nuclear specialist team (photo 7). with Halifax Regional Fire and Emergency in Nova Scotia, Canada. He is a graduate of the Fire Service Management TOXIC GASES Program at Dalhousie University. Prior to joining the fire Flammable gases will reach toxic levels long before they service, Lake served in the Canadian Army as a nuclear, are within their flammable range. CO and H2S sensors are not biological, and chemical defense officer. designed to determine the toxicity of flammable gases. CO is

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COURSE EXAMINATION INFORMATION To receive credit and your certificate of completion for participation in this educational activity, you must complete the program post examination and receive a score of 70% or better. You have the following options for completion. Option One: Online Completion Use this page to review the questions and mark your answers. Return to www.FireEngineeringUniversity.com and sign in. If you have not previously purchased the program, select it from the “Online Courses” listing and complete the online purchase process. Once purchased, the program will be added to your User History page where a Take Exam link will be provided. Click on the “Take Exam” link, complete all the program questions, and submit your answers. An immediate grade report will be provided; on receiving a passing grade, your “Cer- tificate of Completion” will be provided immediately for viewing and/or printing. Certificates may be viewed and/or printed anytime in the future by returning to the site and signing in. Option Two: Traditional Completion You may fax or mail your answers with payment to PennWell (see Traditional Completion Information on following page). All information requested must be provided to process the program for certification and credit. Be sure to complete ALL “Payment,” “Personal Certification Information,” “Answers,” and “Evaluation” forms. Your exam will be graded within 72 hours of receipt. On successful completion of the posttest (70% or higher), a “Certificate of Completion” will be mailed to the address provided.

COURSE EXAMINATION 1) Complacency towards maintenance of equipment often leads to a 7) The fundamentals of gas detection involve consistent maintenance “we’ll figure it out on-scene” mentality. and: a. True a. Training b. False b. Experience c. Accurate interpretation of the calibration procedure 2) What is one recommendation the National Institute of Safety and d. Accurate interpretation of the numbers Health (NIOSH) recommended after a natural gas explosion in Maryland on May 7, 2009 that injured eight firefighters? 8) Firefighters can easily ensure accurate readings by ______the a. Fire departments should purchase gas monitoring equipment for gas monitor and avoiding activities that harm gas sensors all fire apparatus a. Calibrating b. Fire departments should rarely maintain gas monitoring equip- b. Elevating ment due to wear-and-tear on meters c. Reading c. Fire departments should ensure gas monitoring equipment is d. None of the above adequately maintained and firefighters are routinely trained on proper use d. Fire departments should not monitor potentially hazardous 9) Gas sensors start gaining accuracy soon after they are manufac- atmospheres tured as a normal result of exposure to air and other gases. a. True 3) How can fire departments reduce the odds of repeating similar b. False accidents to the 2009 Maryland gas explosion? a. Minimizing the accuracy of their metering equipment 10) The loss of accuracy of a gas meter is called: b. Maximizing the accuracy of their metering equipment a. Meter drift c. purchase more metering equipment b. Sensor drift d. Calling for mutual-aid meters early on in the incident c. Decalibration d. Sensor loss 4) Fire departments are commonly equipped with two popular gas detection devices: the single-sensor gas monitor, or the: 11) ______is one way to compensate for sensor drift. a. Multi-sensor gas monitor a. Purchasing new sensors b. Carbon Dioxide meter b. Routine maintenance of meter housing c. Sulfur Dioxide meter c. Calibration d. Photo-ionization detector d. All of the above

5) Multi-sensor gas monitors are usually equipped with which of the following sensors: 12) Most manufacturers recommend that their gas sensors are calibrated ______and after a significant exposure. a. Lower explosive limit a. Daily b. Oxygen b. Weekly c. carbon monoxide c. Monthly d. All of the above d. Yearly

6) A catalytic bead or electrochemical sensor converts the presence of flammable or toxic gas into an electrically measurable signal on 13) Using expired calibration gas may also cause inaccurate meter most meters used by fire departments. readings. a. True a. True b. False b. False

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14) Exposure to ______can destroy sensors or at least reduce 18) Exposure limits are established by the authority having jurisdic- their accuracy. tion, and are usually adopted from OSHA, NIOSH, or the ACGIH. a. Harmful substances a. True b. Fire b. False c. Water d. Toxic environments 19) ______are the most frequently encountered hazardous materials. 15) The time it takes the sensor to process the gas and display a a. Sulfur dioxides number is called: b. Aromatic hydrocarbons a. Free time c. Flammable substances b. Lag time d. Toxic atmospheres c. Sensor delay d. Sensor interpretation 20) The standard multi-sensor package will not detect: a. Harmful substances 16) The lower explosive limit sensor requires a specific amount of b. Toxic gases oxygen to function properly. c. corrosive gases a. True d. Flammable gases b. False

17) ______and ______sensors routinely produce false positives.

a. CO and H2S

b. CO and O2

c. H2S and LEL d. UEL and LEL

Notes

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