These tests give an objective measure of face fit. They require specialised equipment and are more complicated to carry out than qualitative methods. Quantitative fit testing provides a numerical measure of the fit that is called a fit factor (FF). The fit factor is a measure of how well a particular face piece seals against the wearer's face. A higher fit factor means the face piece achieved good contact between the face seal and the face during the test. The recommended minimum fit factor that should be achieved to pass a fit test will depend on the type of face piece being tested.