Masks and other respiratory protection

Dusts, gases, fumes, mists and vapors are common hazards in workplace air. These can seriously affect the health of workers. Breathing in asbestos fibers can lead to asbestosis and lung cancer while crippling lung diseases can be caused by the inhalation of certain dusts.

Inhaling some chemicals, such as solvents, can damage many parts of the body including the brain. Welding fumes, smoke, mists from spray painting are also serious respiratory hazards and workers should be adequately protected from exposure to any of them.

Protection against respiratory hazards

The most important defence against respiratory hazards is to control the contamination at its source and prevent it from entering the air. This can be done by either substituting dangerous substances with less hazardous ones (particularly where chemicals are used), by isolating or enclosing hazardous operations, or by providing adequate local exhaust ventilation. However, in some situations it may be necessary to wear respiratory protective equipment (RPE). This may be because it is not immediately practical to implement some of the above mentioned measures. Or it may be because access to a contaminated area is needed for a short period, or maintenance operations need to be carried out. In addition, RPE may need to be worn in some emergency situations.

The use of respiratory protective equipment is often favoured by employers because it is generally a cheaper option, when compared with the cost of controlling the hazard at its source. Nevertheless, many employers are not even prepared to commit the resources required for an effective Personal Protective Equipment Program (see later). In some instances, engineering controls may be more cost-effective in the long-term, in addition to improving health & safety in the workplace.

The Australian Council of Trade Unions (ACTU) Health and Safety Policy strongly emphasises the importance of engineering control measures such as hazard enclosure or local exhaust ventilation. It is essential that workers find out all the possible options for preventing an airborne hazard before agreeing to wear respiratory equipment on a regular basis.

It is also essential that any respiratory protective equipment program implemented in a workplace includes air monitoring. Respirators of different types are suitable for atmospheres of specific concentrations only. If the concentration exceeds a certain level, a different type of respirator will be necessary.

This Fact Sheet is intended to inform workers on the different types of respiratory protection and what should be done before you wear them at work.

Types of respiratory equipment

In general, there are two types of respiratory protective equipment - air purifying respirators and air supplying respirators. The latter are either self contained air supply, like what SCUBA divers wear, or are supplied from an external air source.

Air purifying respirators

Air purifying respirators are divided into three categories - those which purify through:

• Filtering self-rescue (these are used for dusts, fumes, fibres, particulates and mists)
• Gas filtering absorption (these are used for gases and vapours)
• Particular filter (a combination of the above two filters)

• Filtering self-rescue
  
  Dust, Fume and Mist Particulate Respirators
  
  Dust, fume and mist particulate respirators consist of a quarter or half face mask and a filter unit. They are basically mechanical filters. They give no protection against gases, vapours or oxygen deficiency.
  
  Care must be taken with the filter and they must be replaced regularly. As the filter becomes clogged, resistance to air flow increases. Apart from increasing the wearer’s workload, this also increases the likelihood of leakage around the mask. (See the Maintenance section of this Fact Sheet for advice on replacement of filters).
  
  There are three classes of filtering self-rescue based on their efficiency in filtering particles from outside contaminants.
  
  For example, Class 3 is the high efficiency type where penetration does not exceed 0.01 %.
  
  That is, when the dust concentration outside is 10 mg per cubic metre, then only 0.001 mg/m3 of dust (0.01%) will pass through the filter into the lungs.
  
  Disposable Respirators
  
  These are generally paper masks, which are only used for non-toxic contaminants (such as house dust).
  
  
• Gas filtering absorption
  
  Gas Masks
  
  The gas filter removes certain gases from the inhaled air and has a limited period of use. Gas masks are full face-pieces attached to a canister, which is mounted on the front, back or chin.
  
  The type of canister depends upon the vapours or gases that need to be removed and it is essential that the correct canister is selected.
  
  These masks must not be used with canisters which have exceeded the recommended life of the absorbent in it (the expiry period varies according to the size of the canister and the type of absorbent).
  
  Gas masks must not be used in oxygen deficient areas.
  
  
  "Escape-masks" are a sub-group of gas masks and are usually a half-mask or mouthpiece respirator.
  
  Chemical Cartridge Respirators
  
  These are similar to Gas Masks, except that the cartridges are smaller. They are available as half-masks, full masks, hoods or helmets and are useful for nuisance exposures to some vapours or low toxicity gases.
  
  Different cartridges are available for different vapours or gases and care must always be taken that the correct cartridge is used.
  
  They must not be used in environments
  
  
  • which are low in oxygen
  • with very toxic substances
  • with substances that will react with the chemical fill
  • with eye irritants or
  • with substances not detectable by smell or taste.
  
  
  
• Particular filter (a combination of filtering and absorption)
  
  Pesticide Respirators
  A pesticide respirator is comprised of a face-piece, an organic vapour canister and an aerosol filter.
  
  

Air supplying respirators

• Self Contained Breathing Apparatus
  
  

  Self Contained Breathing Apparatus provides respiratory protection in any toxic gas or oxygen deficient conditions. The supply of air or oxygen is carried by the wearer. When used with proper protective clothing, complete isolation from the dangerous environment can be achieved. Self Contained Breathing Apparatus are the equipment of choice in emergency or rescue work, as they can operate independently of an air supply, and with no trailing hoses. They have the disadvantages of being heavy, bulky and hot, and are limited in their range by the amount of air carried by the worker. These also require a lot of training in their proper use.

  
  
• Supplied-Air Respirators
  
  These respirators supply air to the wearer through a hose. They may be sub-grouped as:
  
  
  1. Hose masks with blower. These have a full face mask connected by a flexible hose to an air source. The source provides air under pressure by a hand or power operated blower. The inlet end of the air hose must be located away from the compressor.
  
  
  
  2. Hose masks without blower. These are similar to the above, but the air is drawn in by the user's respiratory effort. Hose masks without blowers should not be used with a hose longer than 22 meters.
  
  
  
  3. Air-Line Respirators. These are either full or half-face masks with air supplied through a hose from a compressed air source. They are designed to provide a constant positive pressure inside the face-piece to prevent inward leakage. They may be used with hose lengths of up to 90 metres.
  
  
  
  Hose masks and air-line respirators are the most highly efficient. They should be used where dust, mist, vapour or gas concentrations are immediately dangerous to health. They are light and comfortable and are the best type of protection where long-term respirator use is required.
  
  However, the long hose may be a nuisance or hazard if cut or blocked and care should be taken that no contaminants are allowed into the air source. It is surprising how often exhaust carbon monoxide from the compressor finds its way into the air-line because of improper placement of the air intake valve. Special filters from a compressor should be fitted to any air-supply line to remove oil mists, etc. These should be regularly checked.
  
  

Selecting the right equipment

There are many types of respiratory protection equipment and the correct type must be selected for the job; otherwise it will be useless. Unfortunately, most RPE are selected because they are the cheaper choice and look as though they “will do".

Selection of the right protective equipment is easy, once the hazard is identified. RPE should not be selected unless there is accurate information on its toxicity and on the amount present in the working environment. Therefore, it is essential that air monitoring is regularly carried out, even when RPE is used. If the contaminant levels in the air increase, a different type of respirator or other controls may have to be used.

Standards

The Australian Standard AS/NZS 1715-1994 Selection, use and maintenance of respiratory protective devices should be referred before selecting respiratory protection.

It explains the general principles of respiratory protection and different types of respirators.

The Standard describes in detail the management responsibilities after the purchase of RPE because education, training and maintenance is important for efficient protection.

Fitting

There is no purpose in wearing a respirator if it does not fit, or is worn incorrectly. Faces are different shapes and sizes and respirators come in a variety of brands and sizes.

When respirators are being selected for a workplace, workers should insist that a range of brands and types are available to choose from, and that everyone undergoes a facial fit-test.

Correct fit and comfort are just as important as technical effectiveness

Once a mask which seems appropriate for the individual and task has been selected, the wearer must be shown how to fit it. Seals must be inspected and the rubber must be in good condition. Inlet and exhaust valves should be inspected for correct operation, particularly for blockage or sticking - sweat and saliva often cause them to clog up. The RPE are often made of rubber and this must not be allowed to perish.

Correct fit of a mask requires contact with smooth skin - this makes masks unsuitable for men with beards or moustaches. Even a one day growth of a beard has been shown to allow nearly one per cent penetration of a full face-piece. This is unacceptable with very toxic or carcinogenic substances. Small beards or moustaches which fit inside the face-piece are also unacceptable as they may cause an exhalation valve to fail if a hair lodges in it.

Glasses must not be worn inside a face-piece unless they are specially designed for the purpose, as the ear pieces will prevent a good seal. These face-pieces are also unsuitable for people who wear contact lenses.. Workers who wear glasses or contact lenses should be supplied with air-supplied hoods or helmets.

Users should be provided with instruction about how to replace filters, canisters and cartridges and when to do so. There must be practice drills and periodic refresher training in the use and care of the protective equipment.

Maintenance

All respirators should be inspected at least once per month and cleaned and examined after each use. Face-pieces should be washed in warm water with a detergent, rinsed and air dried. They may be disinfected with hypochlorite (bleach) solution.

Filters and cartridges cannot be disinfected and should be replaced daily or when breathing becomes noticeably more difficult, indicating that the filter is becoming clogged. Respirators should be stored in a dust-proof container or locker.

Training

The first step in training is a full explanation of the types of hazards to be encountered and an explanation of the type of respirator and the reason why it was selected. Next, all wearers should be shown how the respirator works, what it can do, its limitations and how to maintain it. They must be shown how to put it on, to adjust the face-piece for correct fit and how to test for leaks. There must be adequate instructions about how to replace filters, canisters and cartridges and when to do so.


Your employer should regularly check with workers about the effectiveness of using RPE and address any concerns without delay.

References

• Australian Standard AS/NZS 1715:1994 Selection, use, maintenance of respiratory protective devices (Standards Association of Australia, Sydney).
  
  
• Australian Standard AS/NZS 1716:1994 Respiratory protective devices. (Standards Association of Australia, Sydney).
  
  
• Frequently asked questions about Personal Protective Equipment WorkCover NSW, 1995

For further information and advice contact the Workers Health Centre
02 9749 7666
admin@workershealth.com.au

Facts 014 © Workers Health Centre, 1999