• Deficiency of oxygen
• Particulate contaminants
• Gaseous or vapour contaminants

There are two main types:

• air purifying devices
• devices which supply air

Air purifying devices

These devices can not be used in oxygen depleted atmospheres.

Air purifying devices fall into four major categories.

• Dust masks – used for protection against nuisance dusts such as sawdust, chalk, plant-related and sanding dusts. These are generally not suitable for toxic substances
• Gas filters - filter fitted into a half face mask, full face mask or hood, suitable for removing low concentrates of certain gases and vapours. Filters have limited use and storage lives and are specific to certain gases or vapours. They are not generic - a specific filter needs to be matched to a specific make of mask.
• Particulate filters - used to remove finely divided solid or liquid particles from inhaled air. Particulate filters have a prefix 'P' and a number indicating a class corresponding to filtration efficiency against a laboratory challenge aerosol of sodium chloride. P1, P2 and P3 filters roughly correspond to the former L, M and H cartridges. There are three types of particulate filter suitable for filtering finely divided solid or liquid particles, or both, from inhaled air. These are classified, in accordance with tests in AS 1716, as:
  • CLASS (P1) Intended for use against mechanically generated particulates, (for example, silica, asbestos).
  • CLASS (P2) Intended for use against both mechanically and thermally generated particulates, (for example, metal fumes).
  • CLASS (P3) Intended for use against all particulates including highly toxic materials, (for example, beryllium). Class P3 requires a full face mask.

Note: Cotton fibre or plastic foam pads are not permitted.

• Combined gas and particulate filters - filter combinations are used where both hazard types may exist.

Devices which supply air

These include airline respirators and self-contained breathing apparatus. Use of this equipment requires detailed training. Example of use areas may be spray booths, PC4 biohazard labs and sandblasting. Further details are available from UWA Safety and Health.

Factors which influence selection include:

• adequacy of warning available
• type of hazard
• concentration of contaminant
• acuteness of hazard, that is, the effect of short exposure
• time spent in contaminated atmosphere
• nature of the working environment
• activity of the wearer
• mobility of the wearer
• whether for routine or emergency use

If in doubt contact UWA Safety and Health.

Achieving a good facial seal is essential. Facial hair such as beards and sideburns prevent a close fit and spectacles or even facial irregularity may also present problems. Tests involving detection of odour and gross leakage should be carried out as described in AS/NZS 1715.

Training in the correct use of equipment is required by law.

Instruction shall include:

• how to recognise the need to wear the device
• importance of conscientiously wearing the device
• how the device works
• application and limitations of the device
• how to determine if it is working properly
• the time for which the device will give protection
• procedure for dealing with an emergency when the device is being worn
• importance of not removing the device until it is safe to do so
• importance of taking care of the device, such as cleaning, maintenance, storage.

The head of school/section/unit shall ensure that all respiratory protective devices are regularly checked, properly stored and maintained, cleaned and replaced (both mask and cartridges as appropriate) according to applicable standards and manufacturer's advice. Users should be supervised to ensure that any instructions specific to this equipment are followed.