FEATURE


FIT FOR PURPOSE


To ensure that any Respiratory Protective Equipment (RPE) is suitable, it must be adequate for the hazard and suitable for the wearer, task and the environment in which it is to be used.


The adequacy of RPE can be determined by the guidance offered by regulatory requirements. During the current COVID‐19 situation, NHS guidance for certain tasks is to use FFP3 or equivalent product. To make sure that the product is suitable for the wearer, fit testing can be carried out if appropriate.


A fit test determines the suitability of a particular style of the mask to the wearer. If the mask is changed, a new fit test is required. If the wearer changes due to weight loss or gain, facial surgery, or any other changes to the face, a new fit test is required. It should be noted that not every user will fit every mask and not every mask will fit every user. Hence the need to fit test.


TIGHT AND LOOSE‐FITTING RPE Tight‐fitting RPE is equipment that relies on having


a good seal with the wearers face and will need to be fit tested. It falls into two further categories, filtering devices and supplied air devices.


Loose‐fitting equipment is currently not required to be fit tested. It also falls into two further categories, filtering and supplied air devices.


FIT TESTING METHODS There are two types of fit testing, Qualitative and


Quantitative.


Qualitative fit testing (QLFT) is a pass/fail test based on the wearer’s subjective assessment of any leakage through the face seal region by detecting the introduction of bitter or sweet tasting aerosol as a test agent. QLFT methods are suitable for disposable and reusable half masks; they are not suitable for full‐face masks.


Quantitative fit testing (QNFT) provides a numerical measure of how well a facepiece seals against a wearer’s face; this is called a fit factor. These tests give an objective measure of face fit.


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Here, JSP provides a brief guide to the fit testing of respiratory protective equipment.


QNFT methods are suitable for disposable and reusable half masks and full‐face masks. The most common method of carrying out of this test is ambient particle counting. Chamber and controlled negative pressure testing is also available.


HOW IS THE TESTING CARRIED OUT? A qualitative test involves two parts. Firstly, the test


subject’s sensitivity to the test challenge has to be determined. This is achieved by placing a hood over the subject’s head and filling the hood with an aerosol, this can be bitter or sweet tasting. The subject should indicate that they can taste the aerosol.


The second part of the test is carried out after the subject has donned their respirator and other Personal Protective Equipment (PPE) that may interfere with the respirator fit, the hood is placed over the wearer’s head and then a high concentration aerosol is put into the hood. Ensuring that the level of the aerosol is maintained in the hood, a series of exercises are carried out. At any point, if the subject tastes the aerosol the test is stopped. The test can then be repeated.


For a quantitative test, the ambient particle counting method test involves just the one part. Having donned the respirator, it is attached to equipment that samples the air outside the mask and air inside the mask. The subject should also don any other PPE that may affect the face seal of the mask. Samples are continuously taken while the subject carries out a series of exercises. At the completion of the exercises, the test equipment will carry out a series of calculations and a fit factor will be determined.


FIT TEST OR FIT CHECK Fit testing is an initial and a periodic check of the fit


of the mask to the wearer. It should be carried out for each different type of tight‐fitting RPE the wearer is required to use. Fit checking is something that should be carried out prior to fit testing and should be carried out before entering the hazard zone each time the respiratory protection is donned.


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