Dusts vary in size and the finer they are the higher the hazard. Mists result from spraying applications. Fumes are particles that are produced during welding and created by vaporisation. Gasses usually odourless and invisible and replace the oxygen content in the atmosphere. Vapours occurs when solvents evaporate at room temperature general have addictive smell.

Choosing the right protection
Identify the hazard is it a dust, mist, fume, gas or vapour. Assess what the level of contamination is. Compare the levels of hazard to the W.E.L. (workplace exposure limits)   Choose the correct respirator applicable to the hazard. Ensure the user has information on the correct wearing storage and use of RPE.

Products should be chosen by the APF (Assigned Protection Factor) of the product to ensure the level of the hazard is reduced and is providing the wearer with clean filtered air.

Exposure limits
WEL’s (Workplace Exposure Limits) are published by the H.S.E. in the EH40 document providing the concentrations levels that substances should not be exceeded. The respiratory equipment can then be chosen by its A.P.F. (Assigned Protection Factor) to reduce the hazard and provide clean air to the user.

Example: Wood Dust
Measured respiratory hazard = 45mg/m2
WEL (workplace Exposure limit) = 5mg/m2
Divide Hazard Level 45mgm2 by WEL 5mg/m2 = 9
You then have to choose a respirator with an APF greater than 9 which would be a P2.

Fit-testing of Respiratory Protective Equipment (RPE) facepieces
To ensure the wearer has the correct device, the initial selection of RPE should include fit-testing. RPE should have a tight-fitting facepiece (filtering facepieces are usually known as disposable masks, half and full-face masks).
Repeat fit-testing will be needed if anything changes. For example, if the model or size of facepiece is changed or there are significant changes to the individual wearer’s facial characteristics due to weight gain/loss or dentistry.

There are two forms of fit-testing – Qualitative and Quantitative:

Qualitative fit-testing is usually adequate for disposable filter facepieces and half-masks. This can be done as a simple pass/fail based on the wearer’s subjective assessment of the fit and leakage. This method is not suitable for full-face masks.

Quantitative fit-testing provides a numerical measure of the fit known as a 'fit factor'. These tests give an objective measure of face fit. They require specialised equipment and are more complicated to carry out. These methods are recommended for full-face masks.

Disposable Masks  Protect against dusts/mists/fumes and low level vapours P1=4 P2=10 p3=20
Half masks Protect against dusts/mists together with combinations of gases and vapours  P1=4 P2=10 p3=20 A, B, E, K.
Full Face  Masks Protect against dusts/mists/fumes and low level vapours together with combinations of gases and vapours and give eye and face protection  P1=4 P2=10 p3=20 A, B, E, K.
Powered respirators Provide clean air drawn through a filter and can be tailored for a variety of hazards  APF range 5-40
Airline Hoods 
Provide clean air to the wearer from an external source and can also combine eye protection and head protection
APF range 5-40


Assigned Protection Factors & Standards for Respiratory Protective Equipment (RPE) types
Type of RespiratorDescriptionStandardAPF Range
Filtering facepieces for particulates  Provides protection against dust/mists/fumes. Normally intended for 1 day’s use  EN149: 2001  4-20
Filtering facepieces for nuisance gas/vapour    Provides protection against dusts/mists/fumes. Also protection against nuisance level gas/vapour EN149: 2001 4-20 
Half masks (dust)  Provides protection against a variety of contaminants dependant on Filter(s)   EN140, EN143, EN405 4-20
Half mask (gas/vapour)  Provides protection against a variety of contaminants dependant on Filter(s)   EN140, EN141, EN405 4-10
Full face masks (dust)  Provides protection against a variety of contaminants dependant on Filter(s) and protection for the face/eyes  EN136, EN143  4-40
Full face masks (gas/vapour)  -  EN136, EN141  4-20
Powered respirators  Provides clean air to the headpiece by drawing air through a filter. Protection can be tailored to a variety of hazards EN146, EN12941, EN12942  5-40
Airline hood or helmet  Provides clean air to the wearer’s headpiece from an external source of breathable quality air. Can also provide eye/head protection EN270, EN1835, EN139  5-40
Self contained open circuit breathing apparatus 
The top level of protection. For tasks where there is an immediate danger to life or health 
EN1146, EN137
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