Monday, 07 May, 2018
Human lungs have evolved over thousands of years to deal with naturally occurring levels of particles — such as dusts, pollens, small pieces of vegetation and seeds.
We have developed certain protective mechanisms like nasal hairs, mucous-lined airways and even a coughing and sneezing response as ways to control exposures to reduce the chance of significant damage to our respiratory system. These processes can only go so far, and modern industrial processes can expose us to types and levels of substances that do not occur naturally and we have little or no effective defence against these.
The laws of the states and the Commonwealth mandate the use of appropriate strategies to provide a safe workplace, meaning employers are required to use appropriate means to control worker exposures. Therefore, providing respiratory protection for workers can be an important part of the duty of care of the employer.
Ideally, controls will be in place to keep exposures to these airborne contaminants to a minimum eg, using materials that do not create a respiratory hazard, use of extract ventilation, use of sealed delivery and mixing systems etc. Each workplace will have its own problems and hazards and will require assessment by a suitably qualified person to determine appropriate controls and whether respiratory protective equipment is needed.
The challenge is to select and wear the right respirators to make sure workers are protected from these hazards. By wearing a well-fitted respirator 100% of the exposed time, workers can remove or greatly reduce the risk of exposure, both short and long term.
Respirators are designed to reduce and control exposures to substances, aiming to protect the wearer to bring exposure to levels that should not be hazardous.
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 product 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 with the information they need to select and use appropriate respiratory protection products.
A Respiratory Protection Program operating according to the guidance in AS/NZS1715 is needed for workers to achieve a safe, reliable and ongoing level of protection from identified airborne contaminants.
There is a range of other relevant regulations and codes of practice used in various jurisdictions across the country eg, those from SafeWork Australia (see website having links to various Model Codes of Practice — https://www.safeworkaustralia.gov.au/resources_publications/model-codes-of-practice). These codes are applicable across several states and territories while a couple of states have their own corresponding equivalent documents. These all deal at least in part with the appropriate respiratory protection for some specified applications eg, for use with asbestos, in confined spaces, when spraying pesticides or paints containing isocyanates etc.
After identifying the specific types and potential concentrations of the respiratory hazards that will be encountered, suitable respiratory equipment for these conditions will need to be identified. Normally there will be many options, depending on the local conditions, the exposure levels, wear time, cost and other factors.
It is crucial that the wearer uses a respirator with the appropriate performance and rated level of protection to give a suitable reduction in exposures occurring during identified workplace tasks.
It is very common for ‘mask with filter’ products to be selected. These masks are relatively inexpensive and can be suitable to deal with airborne concentrations commonly encountered with many processes. They come in various types, shapes and sizes (eg, disposable, half or full face masks) and these are all covered by the descriptor “tight fitting” — because they all rely on an effective fit of the selected mask on the wearer’s face. This effective fit means the vast majority of the contaminants go into and are captured by the filters and do not bypass these by slipping through gaps between the mask and the face.
As this facial fit performance 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. This process is required by AS/NZS 1715 and the relevant OH&S regulators. Note that no manufacturer is able to make a mask that fits ALL faces and a fit test is the required method to confirm whether the selected mask fits the individual’s face effectively (or not). There is fit-testing equipment available, as well as consultants who can do this testing for you.
Many users of tight-fitting masks overlook this step and may be wearing a mask that does not fit their face effectively, perhaps due to size, shape or non-conformance of the mask with their individual facial contours. They will not be getting the expected level of protection and therefore can be overexposed.
An effective face fit means that facial hair (moustaches, beards, stubble) is not allowed for workers using tight-fitting masks. The facial hair acts to lift the mask off the face and create leakage pathways. So, a clean-shaven policy (ie, be clean shaven at the beginning of the work shift) is needed to be able to have confidence the wearer should be able to get a fit each day.
Besides facial hair, there are other reasons why a half or full face mask may not be acceptable to an individual:
- There may be no tight-fitting mask available that fits and is acceptable comfort wise to the wearer.
- The potential wearer has some physical condition that is not compatible with the increased breathing resistance caused by a filtering mask eg, they have a lung issue or breathing problems and cannot deal with any increase in breathing resistance from a respirator.
- There is a reluctance by the individual to wear a mask eg, claustrophobia, heat issues or compatibility with other PPE also required.
For those individuals who cannot or will not wear a tight-fitting mask, use of a powered air-purifying respirator (PAPR) or supplied airline respirator system, fitted with a suitable headtop (eg, a hood or helmet) can provide an alternative that can give the required protection. PAPRs use a battery-powered fan and filter system to provide clean, filtered air to a headtop and do not rely only on the face seal for performance. Instead, they supply an excess of filtered air into the selected headtop, which effectively prevents entry of the contaminants into the breathing zone. The filtered air is continuously escaping outwards and blocks entry of the outside ‘dirty’ air. Headtops are available with different designs and features eg, hoods, rigid helmets, masks, welding shields, etc.
A PAPR has the following benefits:
- No breathing resistance.
- Powered air delivery creates a moving flow, which creates a cooling effect.
- Can be used with facial hair that does not interfere with the faceseal of the selected headtop.
- The headtop can provide multilevel protection — eg, head, eye/face and/or welding protection as well as respiratory protection.
Another option is a supplied airline respirator. This type supplies compressed air from a clean, distant source through a pipeline and a final filtration step through a flexible hose and air regulator to a suitable mask or headtop.
A supplied airline respirator has all the benefits above plus:
- Does not require a filter that is suitable for all the airborne contaminants present in the workplace air.
- High protection levels according to AS/NZS1715.
- Can use vortex heaters or coolers to ‘air condition’ the filtered supplied air coming into the headtop by up to 250°C.
Employers or workers not familiar with the various factors and product features available with respirators can seek the advice of an occupational hygienist, safety professional or the suppliers/manufacturers to determine the valid options.
A global ISO Standard for Respiratory Protection is currently in development. In the future, this may well change the framework for design and selection of respiratory protective equipment, although arrival is still a number of years away. Advances in materials technology and greater use of electronics will also impact on future product designs.
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