Face Fit Testing serves as a vital method in safeguarding against the inhalation of harmful airborne substances by assessing the effectiveness of respiratory protective equipment (RPE). It is recognised by the Health and Safety Executive as the only means of ensuring that a RPE wearer is adequately protected through the use of RPE. It is a legal requirement under the Control of Substances Hazardous to Health (COSHH) Regulations, the Control of Lead at Work Regulations, the Control of Asbestos Regulations and the Ionising Radiation at Work Regulations all of which are designed to protect workers from hazardous substances encountered in the workplace.

Face Fit Testing evaluates the seal between the RPE's facepiece and the wearer's face, ensuring an airtight fit to prevent the escape of contaminated air into the mask. This is particularly critical when exposed to hazardous substances such as harmful chemicals, dust and fumes which can lead to serious health issues such as respiratory disorders and cancer.

Employers are legally responsible to provide suitable RPE to workers exposed to hazardous substances and to ensure that the equipment fits properly and offers effective protection.  Face fit testing is an integral part of this process, verifying that the RPE is compatible with the wearer's facial dimensions and is worn correctly to establish a secure seal.