The mask FIT test or a respirator fit test is the test to determine whether the mask fits the face of the wearer. Masks are used to keep the respiratory system of the employees separate from the ambient air. In order for this mask to provide an effective seal around it, it is necessary to ensure that it fits properly without leaving a gap on the face. A gap between the mask and the face means that the mask does not provide complete protection for the wearer. Mask FIT tests are performed for this purpose.
These tests are done in several ways. Scientific researches show that if the size and shape of the mask is placed on the face of the employees correctly, the person will be better protected in dangerous environments.
The selection and use of the appropriate mask or respirator is subject to national legal regulations in many countries.
It is not possible for a respirator that does not fit to the face to provide the expected protection. Some respirators must form a tight seal in order to function properly. Otherwise, contaminated air may leak from the respirator and the person may inhale dangerous substances. At this point, employers should also make sure that the respirator is suitable for the employee. For this, mask FIT tests are required. In this way, it is proven that the mask is suitable for the employee and will protect as long as it is used correctly.
There are several methods of performing a respirator fit test or mask FIT test. These are generally two groups as qualitative and quantitative test methods.
Qualitative test methods are based on the response of the person to the taste or smell of a special material leaking from the mask, gas, vapor or aerosols. Such responses are subjective and results are completely subject dependent. The main items selected in these tests are:
In quantitative test methods, an equipment determines the concentrations of a control substance inside and outside the mask or the flow rate of the air flowing under the mask. These test methods give more accurate and reliable results than qualitative test methods. These test methods provide data-based and defensible measurement values. There are two quantitative test methods in itself: Aerosol methods and flow (pressure) methods.
In aerosol test methods, internal and external aerosol concentrations are measured. The aerosol can be an artificially created natural atmospheric component. The ratio of the external concentration to the concentration under the mask is called the adaptation factor. The fit factor should not be less than 100 for half masks and 500 for full face masks.
In flow (pressure) test methods, when a person breathes in, part of the aerosol accumulates in the respiratory organs and the concentration measured while exhaling is lower than during breathing. During inhalation, unfiltered air droplets under the mask do not actually mix with the air under the mask and the measured concentration will be higher than the actual value.
In short, the tests that determine whether the respiratory protective masks are compatible with the face of the wearer or which type of mask are suitable for the person are called the mask FIT test. In practice, using a high quality and reliable mask is not considered sufficient for adequate protection. Because if the mask does not fit on the face of the person, if its design is not suitable for the user's face form, the expected benefit from the mask cannot be achieved and the person faces insufficient protection.
The tightness between the face part of the respirator and the face of the person is tested with the mask fit test. As explained above, the qualitative fit test does not measure the actual leak, but offers a subjective test method. These tests are done with banana scent, sweet and bitter substances and irritating smoke that causes cough. These fit tests are normally used only for half respirators that cover the mouth and nose.
In the quantitative fit test, an equipment is used to measure the actual amount of leakage. There are three quantitative compliance testing methods adopted by OSHA: generated aerosol, ambient aerosol and controlled negative pressure.
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