Many workplaces can have significant concentrations of airborne contaminants and need to control worker exposure to these materials.
While controls like extract ventilation, wet methods or substitution can assist, there are many workplace situations where personal respiratory protective equipment is needed. When selecting a respirator, there are a number of issues to consider. The basis for selection and required performance of respirators in Australia and New Zealand is normally based on the relevant Australian Standards:
- AS/NZS1716 "Respiratory protective devices" - this is the performance standard. It sets out the performance parameters and requirements for the different types of respirators.
- AS/NZS1715 "Selection, use and maintenance of respiratory protective equipment" provides the users of these products with the information they need to select and use appropriate respiratory protection systems.
There are other regulations and codes of practice in place nationally and in each of the States that specify the appropriate respiratory protection for certain specific applications e.g. for use when working with asbestos and when spraying paints containing isocyanates.
After identifying the type and potential levels of the respiratory hazards that will be encountered, suitable respiratory equipment for these conditions needs to be identified. Normally there will be a number of options, depending on the local conditions, the exposures, wear time, cost and other factors.
The most commonly used type are disposable respirators. These are designed to deal with levels of particulates in the workplace air, with some types also having an added small capacity to absorb low concentrations of organic vapours and/or acid gases.
Reusable respirators have a flexible polymer type mask that can be fitted with suitable filters and is held tightly on the face with adjustable straps. The mask can be a half facemask (covering the mouth and nose) or a full facemask which covers the whole face.
Under the testing protocols for AS/NZS1716, filters in respirators are required to meet certain performance levels - this then allows determination of their suitability for use against specific contaminants at various concentrations - as explained in detail in AS/NZS1715.
There are two main types of filters:
a) Particle filters are tested for capture efficiency and there are three classes of particle filters. These are:
- P1 - for mechanically generated particles eg dusts, flour, silica. Suitable for the relatively "large" particles (mostly >1 micron) released in operations like sanding, cutting, sawing, crushing etc.
- P2 – for mechanically & thermally generated particles eg welding fume. These filters have a higher efficiency to deal effectively with smaller, thermally generated particles like welding fume and is also recommended for infection control applications e.g. TB, flu or other infectious diseases.
- P3 – for use with highly toxic materials and/or when a very high protection level is required e.g. beryllium, radioactive particles.
b) Gas/Vapour filters are produced specifically for use against various gases and vapours and are tested and marked accordingly. There are many different types – some common ones are organic vapours (eg solvents), acid gases, ammonia and there are a range of other specific types available. All gas/vapour filters are also rated for their absorptive capacity - in increasing capacity these are Class Aus, Class 1, Class 2 and Class 3 filters.
It is crucial that the wearer uses a respirator with the appropriate filters and rated level of protection to give a suitable reduction in exposure to the worker in the identified workplace task.
These masks (i.e. disposable, half or full facemasks) are described as "tight fitting" because they rely on an effective fit of the selected mask on the wearer’s face so that the contaminants go through the filters and not bypass them by slipping through gaps between the mask and the face.
As this fit is so crucial, AS/NZS1715 states that all wearers of tight fitting masks shall be fit tested to prove that the selected mask can get an effective fit on the individual. No manufacturer makes a mask that fits ALL faces and a fit test is a method to confirm whether the selected mask fits the individuals face or not.
Many users of tight fitting masks overlook this step and may be wearing a mask that cannot fit their face effectively due to size, shape, etc. They will not be getting the expected level of protection and may be overexposed to the contaminants.
This need for an effective face fit also means that facial hair (moustaches, beards, stubble) is not allowed in those areas where the mask seals on the face. The hair acts to lift the mask off the face and create leakage. So a clean shaven policy (i.e. clean shaven at the beginning of the shift) is needed to be able to get a fit each day.
For those workers who cannot get a fit, do not want to shave or have issues with tight fitting options, there are alternatives. Powered Air Purifying Respirators (PAPR’s) are available. These use a battery powered fan and filter system to provide clean, filtered air to a specially designed headtop and do not all rely on the face seal for performance. Instead, they supply an excess of filtered air into the headtop, which effectively prevents entry of the contaminants into the breathing zone. The headtops available for these units cover many different designs like soft hoods, hard helmets, masks, welding shields, etc.
Another option is a supplied airline respirator. This type supplies compressed air from a clean, distant source through a pipeline and a final filter to a flexible hose and air regulator attached to the worker who is wearing a suitable mask or headtop. This solution is applicable for those exposures where there is no suitable filter or the concentrations in the breathing air are very high and make the use of filters unsafe.
Employers or workers who are not familiar with the various factors and product features necessary to choose the correct respiratory protection can seek the advice of an occupational hygienist or safety professional to determine the valid options. Another good option is to seek advice from the suppliers/manufacturers of these products. They can often provide the end user with the information needed to select and obtain appropriate respiratory protection for the task at hand.