The human body can suffer great harm upon contact with liquid chemicals. In work environments where workers are susceptible to this danger, reduction in direct skin contact is a requirement of the protective clothing worn. Liquid penetration resistance testing is determined using procedures as stated in National Fire Protection Association (NFPA) 1971 Standard on Protective Ensemble for Structural Fire Fighting, which references American Society Testing and Materials (ASTM)
F 903, Standard Test Method for Resistance of Protective Clothing Materials to Penetration by Liquids.

A material specimen is subjected to a liquid for a specified time and pressure sequence and observed for visible penetration. A test material sample is placed in the test cell forming a closed chamber for the external side of the material. Thus, the specimen is acting as a partition separating hazardous liquid chemical from the viewing side of the test cell. In use, the viewing side of the test cell is presumed to be human skin. A challenge liquid is introduced into the chamber contacting the material surface. After a 5 minute observation period, the air pressure is raised from 0 to psig for 10 minutes. During this time, the surface of the specimen is monitored for the appearance of liquid. If liquid appears on the surface or if discoloration is noted, the test is terminated. The specimen size of 2.8 in. x 2.8 in. is used in three replications. Results are reported as pass, fail, or not failure.