A qualitative fit test is a simple pass or fail test based on whether the wearer of a mask can detect a test agent. Whilst they are wearing the mask, a test agent is sprayed into a hood worn over the head. If the wearer can detect the test agent then the mask leaks and does not provide a good enough fit.
Two Types of Qualitative Testing
- Taste test - uses either a bitter (Bitrex) or sweet (saccharin) solution. The wearer breathes through their mouth and will taste the solution if the mask does not fit.
- Odour test - uses isoamyl acetate (banana oil). If the wearer can smell the isoamyl then the mask does not fit.
Not All Masks Can be Tested Using This Method
The qualitative test is suitable for disposable half masks and re-usable half mask respirators only. Full face masks (supplied air or filter) cannot be tested using this method. Furthermore, the taste test and odour test are suitable for different types of half masks:
- Taste test - disposable half masks (FFP1, FFP2 and FFP3) or re-usable half masks fitted with either a particulate or combined filter.
- Odour test - re-usable half masks fitted with a type A organic vapour filter.
CSTS uses the taste test with Bitrex solutions. The test is carried out using a kit which contains a hood, a bottle of both weak and strong solutions of Bitrex and two hand pump nebulisers.
The Sensitivity Test
The first part of this method is the sensitivity test, which determines the wearer's sensitivity to the solution. The fit test operator places the hood over the wearer's head, initially without a mask (as shown). The operator then places a small amount of the weak solution of Bitrex into one of the nebulisers and delivers a number of 'pumps' of the weak solution into the hood.
When the wearer can detect the Bitrex at the back of their throat, the wearer raises their hand. This shows the operator the number of pumps that they need to deliver into the hood in order for the test to be effective.
Some wearers cannot detect the solution. If this is the case, the operator will advise the wearer that this test method is not suitable for them and to try a quantitative test instead.
The Fit Test
During the fit test, the operator places the hood over the wearer's head whilst they are wearing their mask. The wearer carries out a series of seven different exercises (e.g. moving head from side to side, talking, heavy breathing etc) whilst the operator delivers a measured number of 'pumps' of the strong Bitrex solution into the hood. If at any point the wearer detects the Bitrex then the test is a fail. In this situation the fit test operator will ask the wearer to wash their mouth with water and the test can be repeated after 30 minutes either by using the same mask after re-adjustment or by using an alternative mask.
The Breakthrough Test
If at the end of the test the wearer cannot detect the solution, the test is a pass. The operator will then ask the wearer to place one finger under the mask to carry out a break seal test to ensure the wearer can detect the solution.
This test can be a useful training aid - by breaking the seal and being exposed the Bitrex, the wearer understands the level of protection afforded by a well fitting mask.
Other Points To Remember
FACIAL HAIR - The the wearer must be clean shaven where the mask seal meets the face, this is because stubble or facial hair will prevent the mask from sealing correctly against the face.
SMOKING / EATING / DRINKING - The wearer must not smoke for 60 minutes prior to the test, or drink or eat at least 15 minutes (except water) prior to the test.
PPE OR OTHER EQUIPMENT - During the test, the wearer should wear any other PPE (Personal Protective Equipment) or similar, that might be worn with the mask to ensure there is no effect on the seal.