The CBRN (Chemical, Biological, Radiological, and Nuclear) Gas Mask Resistance Test System is a portable instrument that tests the fit of a CBRN gas mask on an individual soldier. The test results are displayed on the screen as a numerical fit factor. The gas mask fit tester does not require the use of aerosol test chambers or tear gas chambers to assess the suitability of the mask. It can be used almost everywhere - in places where gas masks are issued, at training facilities and even in the field.