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Respiratory Protection
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. It is 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.
Types of Respiratory Protection
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 the following categories - those which purify through:
- Filtering self-rescue used for dusts, fumes, fibres, particulates and mists and are basically used for mechanically generated particles. These include the general disposable paper masks which are used for non-toxic contaminants.
- Gas filtering absorption used for removing gases and vapours from the inhaled air. These have limited periods of use. The filter used will depend upon the vapours or gases that needs to be removed and it is essential that the correct filter is selected. These must not be used where they 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). These filters must not be used in oxygen deficient areas.
- Chemical cartridges are useful for nuisance exposures to some vapours or low toxicity gases and different filters are available for different vapours or gases and care must always be taken that the correct cartridge is used. Generally these should 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 are a combination of filtering and absorption. These filters can be used with either the half mask or full face respirators.
Air supplying respirators
Self Contained Breathing Apparatus
- Provide 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.
- They 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:
- 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.
- 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.
- 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. Special filters from a compressor should be fitted to any air-supply line to remove oil mists, etc
?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.
Source:- www.workershealth.com.au/facts014.html
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