It’s clearly recognised that we need clean air to survive and that exposure to toxins could cause irreparable damage to our health, but sometimes respiratory risks are not obvious or the damage to human respiratory systems occurs over a longer period of time, which is why choosing suitable respiratory protection is important for long term worker health.

AS/NZS 1715:2009 which covers the selection, use and maintenance of respiratory protection equipment states: “The effective management of risks to health is achieved by identifying the hazards, assessing the risk associated with those hazards and controlling the risks to health”.

The steps needed to ensure a safe respiratory working environment are:

  1. Undertake a risk assessment to identify the hazard and if possible remove or reduce the hazard, which is always preferable to using Respiratory Protective Equipment (RPE). If this is not possible, appropriate RPE will need to be selected and implemented, to prevent inhalation of contaminated air.
  2. A clearly defined set of selection steps must be followed to determine the type of RPE that is best suited for the job and the contaminant.

Respiratory protective devices are classified into two main groups; Air Purifying Respirators (Filtering devices) and Air Supplied Breathing Apparatus.

In addition to identifying the hazard, AS/NZS 1715:2009 states that;

  • All users must be trained to use RPE
  • RPE must fit properly to prevent leaks around the edges
  • Fit-testing must be done before first wearing a tight fitting facepiece
  • Beards, moustaches, sideburns, stubble & long hair are not allowed when wearing a tight fitting facepiece
  • Cleaning and maintenance of RPE is required.

 

The Three Main Types:

Filtering Facepiece/Disposable Respirators

  • Ideal for most industries and applications where wearers require particulate protection e.g. dusts and mists
  • A choice of cup-shape or flat-fold, valved or unvalved and also the option to protect against ozone and nuisance levels of organic vapours and acid gases
  • Lightweight and maintenance free
  • Comfortable, convenient and easy to use

Reusable Half and Full Facepiece Respirators

  • Offer protection against particulates, gases and vapours and combinations of the two
  • These respirators have integrated or replaceable filters and parts. They may be cleaned, stored and reused provided they are in good condition
  • Full facepiece respirators also offer integrated eye and face protection
  • Many models are fully maintainable

Powered Air & Supplied Air Systems

  • Offer protection against dusts, mists, fumes, gases, vapours and combination hazards e.g. paint spray
  • Can offer integrated eye, face, head, neck and hearing protection in one system avoiding incompatibility issues between items of PPE
  • Modular system allows you to mix and match parts as your environment or application changes, giving you the ultimate in flexibility and ease of use
  • No increase in breathing resistance means more comfortable and longer wear time
  • Usable by a wide range of users regardless of facial characteristics; shape, size etc.


Airborne Hazards

Brick Dust

  • Brick dust and ash contains very fine particles of silica which can be breathed deep into the lungs and scar the delicate tissue (silicosis); exposure may also increase the risk of lung cancer.

Cement Dust

  • Some cement processes can also release very small particles of silica which can be breathed deep into the lungs and scar the delicate tissue (silicosis); exposure may also increase the risk of lung cancer.

Wood Dust

  • Exposure can cause occupational asthma in some individuals as inhalation of wood dust particles may initiate an allergic reaction causing them to become more sensitive in the future. Dusts from hardwoods may also cause cancers of the nose.

Lead

  • Dust and fumes inhaled from industrial processes involving lead or lead compounds may be absorbed and circulate in your blood. Lead can be excreted but it can also be stored by the body. If the amount of lead in your body is too high, it can cause symptoms such as headaches and nausea. If uncontrolled, long term exposure can damage vital organs.

Silica

  • Very small particles of silica dust, called respirable crystalline silica, can be breathed in and may reach deep into the lungs where it can scar the delicate tissue (silicosis) resulting in difficulties breathing. Long-term exposure to crystalline silica may also increase the risk of lung cancer

Flour Dust

  • Inhalation of dust particles from flour can cause bronchitis and irritation to the nose and airways. In some people, exposure may cause occupational asthma, wheezing or serious breathing difficulties.

Welding

  • Inhalation of some metal oxides found in welding fumes can lead to metal fume fever - the symptoms are short term but include coughing, headaches and fever. Exposure to certain nickel and chromium compounds found in some welding fumes may increase the risk of lung cancer.


How gas and vapour respirator cartridges work

Gas and vapour respirator cartridges help reduce user exposure to many different organic vapours. To achieve this objective, respirator cartridges are filled with a material called activated carbon. Activated carbon is typically made from coal or renewable resources like wood or coconut shells. It is “activated” by heating the material in nitrogen or steam at approximate temperatures of 800 – 900°C. The resulting material has a significant number of micropores ideal for removal of organic vapours by adsorption. Adsorption (which is distinct from absorption) is the adherence of gas or vapour molecules to the surface of the activated carbon. The attractive force between the activated carbon and the chemical molecule is a relative small, weak physical force. These micropores can be measured and optimized for specific product needs and performance.

The activated carbon sorbent bed can be impregnated with chemical reagents to remove specific gas and vapours by chemisorption. Chemisorption is the formation of bonds between molecules of the impregnate and the chemical contaminant. These bonds are much stronger than the attractive forces of physcial adsoprtion. The binding is usually irreversible.

Organic vapours are predominantly removed by adsorption. When organic vapours are drawn through a gases and vapour cartridge, the air is filtered as vapours condense into the carbon pores. Vapours move through the cartridge from one pore to the next. This occurs more quickly for small volatile vapours with lower boiling points (e.g., acetone). Some migration of organic vapours can even occur during storage, so care must be taken before reusing the cartridge. The effective service life is the time until vapours begin to exit the cartridge.

Unlike particle filters, service life is not indicated by change in breathing resistance. Instead, cartridges must be changed according to local regulations; or the established filter change schedule. If after establishing the change schedule; the contaminant can be detected sooner inside the respirator by irritation, taste or smell; the change schedule must be adjusted to a shorter change frequency

Activated carbon by itself cannot adsorb other types of gases or vapours such as acid gases, ammonia, formaldehyde, etc. In some cases, additional metals and salts are added to the carbon to selectively remove these compounds. For this reason, 3M offers a variety of cartridges and facepieces to help protect workers in different environments and satisfy personal preferences.

AS/NZS 1716 uses a classification system to identify the different types of contaminants these filter cartridges capture. 3M Australian and New Zealand rated Filter cartridges follow this marking and colour coding system.


How do particle filters work?

A bed of randomly oriented fibres is used to create the filter. Treated fibres can be used to attract and trap particles as they flow into and through the filter material. Increasing the thickness and capture effectiveness of the filter material increases the filter efficiency at capturing particles. Particle filters are tested according to AS/NZS1716 Section 4.3.5 and Appendix I and L.

The physics of particle capture indicates that the particle size range 0.02-0.2 micron equivalent diameter and a mass median particle diameter of approximately 0.3 to 0.6 μm is the most difficult size range to capture. The filter is tested with a sodium chloride challenge aerosol consisting of particles mainly of this size. There are four common mechanisms of filtration being interception capture, inertial impaction, diffusion capture and electrostatic attraction

In practice, particle filters designed for respiratory protection will capture particles of all sizes – the major difference is the relative performance in the range between ~0.1 and 1 um. Each class of filter must perform above a certain level against the test aerosol to be then classified under AS/NZS1716 as explained below.

 

P1/P2/P3 explained

A P1 is an AS/NZS1716 rated particle filter for use with mechanically generated particles e.g. particles generated by crushing, grinding, drilling, sanding, cutting, etc including silica, wood dust, mists from spraying.

A P2 is an AS/NZS1716 rated particle filter for use with mechanically and thermally generated particles e.g. welding fume. These are also the recommended type for use with airborne particles that may contain biological hazards.

A P3 filter is the highest efficiency particle filter class and is used for particulates that are of high toxicity or at high concentrations. The benefit of this high efficiency filter can only be achieved on a full facepiece respirator system.

 

How long do particle filters last?

As particle filters load up with the contaminant, they actually become more restrictive to the passage of particles and can be a better filter. However, they also become harder to breathe through. The wearer will notice this increased load and at some point decide that the restriction is too high and will then need to change the filter. How soon this occurs will also be dependent on the amount of particles in the breathing air. A very dusty job will obviously clog the filter up more quickly than a relatively less dusty job. The change decision point will vary from individual to individual as some people are more sensitive to the increase in breathing load than others.

In summary, the filter should be changed when the breathing resistance becomes excessive to the wearer OR if the filter is damaged in any way e.g. by welding sparks.

 

When should particle filters NOT be used?

There are several applications where particle filters should NOT be used:

  • When the ambient Oxygen level is not guaranteed to be > 19.5%. Filters do not create oxygen.
  • For the capture of gases or vapours - these need a specifically rated gas/vapour filter.
  • When the airborne particulate contaminant concentrations are high i.e. greater than the standard allows for that respirator type.
  • When Government Regulations require use of airline or other specific type of respirator for specific applications

For further information, check out 3M Safety's resources