Unit 5 Control Measures

UNIT 5 CONTROL MEASURES

Principles of Control: Many different hazards are encountered by workers in Canadian workplaces ranging from exposure to compressed gases, flammables and explosives, corrosives, poisons, infectious materials, carcinogens, radiation, heat, noise, vibration, and danger of physical injury. A workplace hazard can be controlled in many different ways, depending on the nature of the hazard and the process that causes it, however, each control measure must meet the following requirements: 1. It must control the hazard so that workers' health is no longer endangered. 2. It must allow workers to do their jobs without excessive discomfort, e.g., full rubber acid suits can be worn for emergencies or short duration jobs but are unreasonable for long periods of time. 3. It must protect all workers who may be exposed, not just the one handling the hazardous product. 4. It must not create a hazard for the surrounding community, e.g., ventilation systems should be equipped with scrubbers to remove hazardous substances from their exhaust rather than just dump dirty air into the neighborhood.

Location of Controls: Hazard controls can be located at 3 places: 1. at the source, where the hazard begins 2. along the path of the hazard en route to the worker 3. at the worker The most effective location of a control is at the source! Controls tend to be less effective the farther they are from the source.

5 - 1 At the Source At the Worker Along the Path

1. Control at the Source: Control of a hazard at its source means that the hazard is :

· eliminated from the workplace altogether; or

· isolated (completely separated) from the worker Control at the source is by far the best method of control, and is the only method acceptable for control of carcinogens (cancer-causing agents).

-elimination -- means that either the operation is stopped permanently (which is usually not practical), or a substitute is used in place of the more hazardous material. Examples of elimination by substitution are listed.

· Benzene -- a carcinogenic substance used as a solvent in paints and other coatings-- has been replaced by less-toxic solvents such as mineral spirits and toluene.

· Asbestos, which has been proven to cause lung cancer, has been replaced by mineral wools such as glass fibers or rockwool in various applications such as insulation.

· Sandstone grinding wheels which give off toxic silica dust, can be replaced by less toxic aluminum oxide wheels.

· The danger of silicosis, the disease caused by silica in the lungs, can be avoided by the use of steel shot for sandblasting.

· White paint can be produced with titanium or zinc oxides instead of highly toxic lead oxide pigments.

· Water-based coatings are continually being improved to replace organic solvent-based coatings to reduce exposure to volatile organic compounds (VOC's), as in latex paints, varnishes, and asphalt sealers.

5 - 2 Caution -- Safer is not necessarily Safe:

SUBSTITUTION Even the "safer" substitutes can still be hazardous if not handled correctly. Although toluene is non-carcinogenic, it, like most organic solvents, cause liver damage in high concentrations. Recent studies of animal exposure to fiberglass have shown some evidence BENZENE XYLENE of lung cancer like that produced by asbestos. - isolation -- means completely separating the worker from the source or the source from the worker. Isolation usually involves some form of "engineering controls". Examples of isolation follow.

· Open tanks or process vessels can be enclosed (covered) and a ventilation system can be connected to the tank to prevent the escape of gases.

· Workers can be isolated from hazardous fumes, by buiding air conditioned control rooms in chemical plants. With clean air being continually pumped into the control room, a positive pressure is maintained in the room so that only clean air escapes but no fumes enter.

2. Control Along the Path: Control along the path between the source and the worker is usually done by one or more of the following methods:

· local and / or general ventilation

· barriers

· housekeeping

5 - 3 - local ventilation -- means using fume hoods, located immediately above or near the source to draw away hazardous fumes. Local fume hoods are common in laboratories, paint spray booths, over hot ovens and welders. A properly designed local ventilation system can be very effective in controlling airborne hazards in the workplace. The air from these fume hoods should be directed through some type of scrubber or air purifier (e.g., electrostatic precipitator, bag house, or cyclone separator) before exhausting the air to the neighborhood!

- general ventilation --, also called dilution ventilation, generally uses a fan or blowers to blow the dust or vapour away from the worker. This dilutes the concentration to which the worker is exposed by spreading it through the rest of the workplace. Obviously, this would only be an acceptable method for non-hazardous, nuisance dusts and odours.

- barriers -- are usually portable screens used to deflect hazardous agents like noise, heat, sunlight, welding light, or radiation away from workers.

- housekeeping -- means proper cleaning of the workplace, disposal of wastes and clean-up of spills. Vacuum cleaners should be used instead of brooms because they remove the substance from the workplace, while brooms may stir it up and spread into the air where it may be inhaled by workers.

3. Control at the Worker: Control at the worker is the least satisfactory control method because it is farthest from the source and does not eliminate the hazard from the workplace. Control at the worker should be used as a last resort as when engineering control are impossible or impractical.

5 - 4 There are 2 kinds of control at the worker.

· administrative controls

· personal protective equipment

- administrative controls -- are the rules and procedures that control the worker rather than the hazard. Administrative controls can limit an employee's exposure to a hazard by reducing the time one spends on a particular task. For example, once employees approach their maximum permissible exposure, they are transferred to another job or area of the plant. This is commonly done in large chemical factories, where there is a large pool of skilled workers who can do job rotation. Medical checkups may be used for screening employees, i.e., to hire new employees who do not have high sensitivity to dusts (if your workplace is dusty) or to know when to rotate employees to new locations. Workers exposed to high temperatures may be given frequent breaks. Cleaning and maintenance of closed chemical vats can release large amounts of toxic material and should therefore be carried out on weekends or at night when as few workers as possible will be exposed to the hazards. Administrative controls do not control hazards, they only control who shall be exposed and for how long.

- personal protective equipment -- is the clothing, hearing protection, respiratory protection, etc. worn by workers in the presence of hazards. When it is not feasible to control the environment by elimination, isolation, ventilation, or some other control measure, it may be necessary for the worker to use personal protective equipment. Personal protective equipment is considered the control method of last resort behind engineering and

5 - 5 administrative controls. Since these protective devices do not eliminate the hazard, failure of personal protective equipment or its misuse may lead to high worker exposure. Personal protective equipment is used:

· when engineering controls do not exist for the process or are impractical as when a particular maintenance job is only done a few days per year.

· when engineering controls are inoperative due to a temporary breakdown

· when there is an emergency, i.e., a spill or a leak.

The most commonly used personal protective equipment, (other than safety shoes and hard hat, which are standard equipment), include:

· safety glasses, monogoggles, or face shields

· hearing protection

· respirators and masks

· chemical resistant gloves, rubber overboots, and rubber suits

Whatever personal protective equipment is selected, it is most important that it is: a) worn when needed (foremen and safety reps need to enforce this), b) fits properly (workers need to be fit-tested for equipment and shown how to use it and know when it needs cleaning or replacement), and c) correctly chosen for the job. The MSDS sheet will be of assistance in specifying what type of respirator or glove is needed. Alternately, the manufacturer or a safety supply store/catalogue can give advice.

5 - 6 Hearing Protection:

Three types of hearing protection devices are available for use when it is impossible to reduce noise to safe levels by engineering methods: ear plugs, ear muffs, and "canal caps" (sound band).

- ear plugs -- are available as reusable rubber plugs or as disposable urethane foam plastic plugs. Both of these are designed to fit snugly into the ear canal. They work best for reduction of high frequency noise; about 30 dB maximum reduction, but far less for low frequency noise. Unfortunately, plugs are generally uncomfortable to wear.

- ear muffs -- have hard plastic shells which completely cover the ear and are sealed to the head with a soft rubber cushion. They are held in position by a sprung headband. Although heavier and bulkier than ear plugs, they give much better protection and are more easily fitted. Ear muffs are available with a frame that connects tightly to the hardhat. Many workers find that ear muffs are hot and restrictive to wear.

-canal caps -- seal the opening of the ear canal with a soft rubber cap which is held in place by a plastic band that fits either over the head or under the chin. It is light weight, does not restrict motion, and easily put on or taken off. The pressure they apply grows uncomfortable in time, making them more suitable for short term use.

When selecting hearing protection, the aim should be to reduce noise to below the danger level of 85 dB. The following table show the average reduction in noise levels in dB obtained by various hearing protection at different frequencies.

5 - 7 Frequency (Hertz) 250 500 1000 2000 4000 plastic ear plugs 12 14 18 27 31 lightweight ear muffs 13 20 27 35 42 heavy weight ear muffs 25 33 39 40 45

Discomfort is the main objection to wearing hearing protection so employers should make several different types available to employees. The best ear protector is ultimately the one that fit the worker best and he/she will wear.

Respiratory Protection: Respiratory protection devices are best suited for occasional / intermittent use for jobs where other controls (isolation, ventilation, etc.) are insufficient. Examples include short-term handling of toxic chemicals, spray painting operations, grinding operations, emergency and rescue work.

Good respiratory protection is difficult to achieve for several reasons: - different types of hazards require different equipment - workers are handicapped (laboured breathing, hampered speech, discomfort) - it is difficult to avoid leaks

Respiratory protection is needed for 3 kinds of atmospheres: 1. oxygen deficient 2. hazardous dust, mist, fumes, smoke 3. toxic gases and vapours

5 - 8 There are basically 2 types of respiratory equipment:

· respirators -- which remove contaminants from air

· breathing apparatus -- which supplies clean air Some are available as half-masks covering only the nose and mouth while others are full-masks covering the entire face. All types must fit snugly, and this makes them uncomfortable to wear. A good seal is almost impossible for workers with beards or glasses.

- respirators -- of any kind require a minimum concentration of 16% oxygen content for safe use.

cloth chemical-cartridge canister masks filter masks filter masks

· Cloth masks are only good for nuisance dusts because they have leakage rates up to 15%. They are not for toxic dusts or very fine dusts (dusts <1 micron are most damaging to the lungs).

· Chemical-cartridge filter masks are half-masks which can absorb toxic gases like acids, organic vapours, ammonia, etc. They are usually O.K. for up to about 0.1% vapour in air and allow about 5% leakage rates.

· Canister filter masks are full-face masks with a large capacity filter attached to the chin of the mask or to a hose connected to the mask. These will withstand up to about 1% vapour for about 30 minutes. They typically allow only 0.25% leakage rates.

None of these respirators are suitable for conditions which are immediately dangerous to life and health (IDLH), because if they fail or become exhausted (used up), the worker is in immediate danger.

5 - 9 breathing apparatus -- supplies clean air to the worker by a airhose/airline or directly from compressed air tanks which the worker wears on his/her back.

· Airhose breathing apparatus may be supplied from a compressed air cylinder or from an air compressor. The air compressor must be designed and maintained to exclude oil droplets, carbon monoxide, and dust. Airhose breathing apparatus is commonly used for sand blasting, spray painting, welding, and cutting operations.

· SCBA (self contained breathing apparatus) uses small compressed gas cylinders worn on the back of the worker. They provide 20-40 minutes of breathing time for escape, rescue, spill clean-up or other emergency. These are the only equipment suitable for IDLH conditions.

self contained breathing apparatus SCBA

5 - 10 EXERCISE FOR UNIT 5

1. Select the requirements of a good control program. a) the cheapest b) protects exposed workers c) relies on "ppe" rather than ventilation and isolation d) allows workers to do the job without additional discomfort e) uses the most expensive technology available f) does not create hazards in the surrounding community g) waits until the best technology is available before controlling hazards

2. Select the most effective control measure. a) at the source b) along the path c) at the worker

3. Name 2 kinds of "control at the source". a) ...... b) ......

4. Name 4 kinds of "control along the path". a) ...... b) ...... c) ...... d) ......

5. Name 2 kinds of "control at the worker". a) ...... b) ......

6. Answer the following as true (T) or false (F)...... a) Ear muffs provide more hearing protection than ear plugs or canal caps (assuming that they are all fitted properly)...... b) Respirators such as masks and chemical filters do not protect the worker when the oxygen level is less than 16%...... c) Air hose type breathing apparatus will protect a worker when conditions are immediately dangerous to life and health (IDLH).

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