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May 29, 2007

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The choice is yours

Making the right respiratory protective equipment (RPE) selection can mean the difference between safety and health or occupational illness, and, in some instances, even death, explains Greg Barber.

From the use of ammonia in agriculture through to xylene in utilities, there can’t be many areas of industry that are not touched by the need for RPE. The good news for wearers of RPE is that technology, in the form of new materials, revolutionary designs and lighter construction, has helped to improve both comfort and performance, making the use of RPE much more acceptable and, indeed, widespread. The bad news is that there are now more masks and respirators to choose from than ever before.

According to HSE reports, UK industry spends around £250 million on RPE each year. If this RPE is not suitable for both the wearer and the application, not only will some of this money be wasted, but the RPE wearers will be exposed to significant health risks.

A full risk assessment, including the risks of engulfment or entrapment, should always be carried out prior to entering a contaminated area, and this is clearly set out in CoSHH and European legislation. From this, an appropriate selection of all forms of personal protective equipment (PPE) can be made.

This article highlights the differences between filtering half-mask and full-face respirators for use with dusts, mists, fume, gases and vapours and explains the need to both use and maintain RPE correctly. It does not cover breathing apparatus, personal escape sets or airline systems which should be worn in very different applications and where the air is immediately dangerous to life and health (IDLH).

Particulate respirators

Designed for use with potentially hazardous dusts, mists and fume, particulate respirators are different to those required for use with gases and vapours. They work by forming a physical barrier against dusts, mists and fume and are classified as providing protection levels of FFP1, FFP2 and FFP3, being 4, 10 and 20 OEL respectively. For this reason, it is obvious that a simple nuisance dust mask should never be used with anything other than large, non-toxic particulates or nuisance odours as it will not stop smaller, potentially harmful particulates from entering the respiratory system.

If a particulate respirator is to be used for a single, short duration project or, for example, be worn by a sub-contractor on a construction site, a disposable version can be selected. If, however, the same worker is going to be returning to the same task it would probably make more sense to opt for a reusable model. The use of disposable or reusable respirators can have long term cost implications as well as an effect on maintenance and record keeping requirements and the decision should be made with those in mind. In addition, and of real benefit in hot and humid environments as well as in arduous applications, certain respirators can be supplied with exhalation valves.

Where combination hazards exist, however, it is sometimes necessary to combine both a particulate and a gas and vapour filtering facepiece. Using one or twin filter cartridges, these are known as single or dual filter respirators and can be supplied with half or full face masks or in powered air versions.

These types of respirator can be used to protect against the asthmatic type reactions caused by exposure to substances in the workplace which are known as occupational asthma. This can also lead to hypersensitivity, i.e. sensitisation such as that experienced by welders with metal fume fever and farmers with farmer’s lung disease. At this point even a short, further exposure at low levels could be sufficient to bring on a severe respiratory attack. Symptoms usually appear within five to six hours of exposure and are similar to flu. This can lead to difficulties in breathing, chronic asthmatic wheezing and, in severe cases where people already suffer from bronchial ailments, the effects may be fatal. Depending upon the substance involved, other exposures can lead to pneumoconiosis and fibrotic pneumoconiosis which includes silicosis and asbestosis.

Powered air

Powered air purifying respirators can be supplied complete with a variety of hoods, helmets and visors to provide application-specific protection against hazardous particulates as well as gases and vapours.

They are recommended for specific applications such as when working with asbestos or where the type of work may place undue strain on the wearer’s lungs. By way of explanation, the HSE guide, ‘Selection of Suitable Respiratory Protective Equipment for Work with Asbestos’ states that users should first consider RPE with the highest protection factor (PF), then match it to the job, work-related factors and the wearer. (On this basis, self-contained breathing apparatus would be the initial choice but, as it would only provide around 15 minutes of breathing air for actual stripping work, it would be considered inappropriate for most applications. At the other end of the scale, the guide also raises concerns that unpowered full-face masks with P3 filters would place demand on the user’s lungs when compared to a powered version).

Therefore, the HSE guide states that a TM3 power assisted respirator with full-face mask and P3 filters would be the choice for those without beards. For those with facial hair, a TH3 powered hood would be suitable.

Gas and vapour respirators

Industrial gases and vapours can be grouped into different categories – each of which has very different effects on the human body. For instance, while not usually life-threatening, the presence of a simple asphyxiant such as carbon dioxide can displace oxygen in the air to such an extent that the lack of oxygen can, in itself, be dangerous.

Hydrogen sulphide and other chemical asphyxiants can be IDLH in that they interfere with the transportation of oxygen within the body and can cause giddiness and headaches before eventual collapse. Irritants such as chlorine can cause ulceration of the throat, watering eyes, sneezing and coughing and, where escape is difficult, breathing can become severely restricted and exposure could prove to be fatal. Hallucinations can follow exposure to high concentrations of narcotic substances like tetrachloroethylene.

Gas and vapour respirators combine a half-mask or full face mask with a filtering device. These filter

cartridges are colour coded for each specific filter type (see table 2).

Each of these filters can also be used in combination to protect against more than one hazard at a time. For example, half masks can be supplied with an A2-P2 filter or a multi-range A2 B2 E2 K2 Hg and P3 filter.

Use and maintenance

The performance of a respirator is dependent upon a good fit and an effective face seal. Any DIY modifications can easily render the respirator useless and should be avoided at all costs. Likewise, users should be aware that wearing a respirator upside down, without just one strap or with loose straps can seriously erode the protection factor.

Users should be trained in the use of RPE and should know how to perform a fit check. They should also be advised to check the fit and, where appropriate, the air flow, every time they don a respirator. Those with facial hair or stubble should opt for a hooded variety as a good facial seal will be difficult if not impossible to achieve. Compatibility with other PPE such as goggles, helmets and spectacles should also be considered carefully.

Only the right filters for the hazard and task should be fitted and any dirty, damaged or incomplete masks should never be worn. Filters should be changed in accordance with the type being used, i.e. A1 filters should be changed at least every two days, A2 filters at least once a week. Others should be changed when breakthrough occurs, i.e. when the contaminant can be detected by either taste or smell. Users should always fit two identical filters to a twin filter mask, at the same time, and gas and vapour respirators should not be used to protect against particulates without an FFP filter.

Disposable particulate masks are designed to be thrown away after every use and reusable versions should be cleaned and stored away from contaminants (in accordance with the manufacturer’s instructions).

Users should also be instructed to adjust and fit all the straps, nose bridges and head harnesses correctly and be encouraged not to wear respirators loosely under their chin during breaks. If they do, they will run the risk of contaminants entering the inner facepiece and being breathed in next time the mask is worn.

Powered respirator wearers will want to ensure that the battery is charged and, as with all respirators that are fitted with valves and vents, that they are fully functional and are not clogged with dirt.

By keeping a small inventory of spare parts, valves, together with face seals and worn or damaged parts, can be easily replaced as and when necessary. As an added benefit, some respirators now feature an integral barcode which means that not only is the mask uniquely identifiable and, therefore, more hygienic in use, but it can also be easily tracked for inventory and maintenance purposes.

Approaches to managing the risks associated Musculoskeletal disorders

In this episode of the Safety & Health Podcast, we hear from Matt Birtles, Principal Ergonomics Consultant at HSE’s Science and Research Centre, about the different approaches to managing the risks associated with Musculoskeletal disorders.

Matt, an ergonomics and human factors expert, shares his thoughts on why MSDs are important, the various prevalent rates across the UK, what you can do within your own organisation and the Risk Management process surrounding MSD’s.

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