ASTM Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Synthetic Blood Using a Mechanical Pressure Technique (F 1819) is a new barrier test method that applies predominately mechanical pressure to the material and synthetic blood until penetration is visible. A modified version of F 1819 uses a sensor test head to detect penetration. ASTM Test Method for Resistance of Materials Used in Protective Clothing to Penetration by Synthetic Blood (F 1670) applies 13.8 (2 psi) of predominately hydrostatic pressure to the fabric, producing a pass/fail penetration result. A modified version of F 1670 applies different amounts of hydrostatic pressure to the fabric in sequential increments for 30 seconds until penetration occurs. The barrier properties of 14 different materials were measured using these methods. The results indicated that materials reinforced with films, coatings, or membranes passed F 1670 and reached the highest pressure level on F 1819 and modified F 1670 without penetration. Single-layer and fabric reinforced gowns exhibited varying degrees of resistance to synthetic blood. Results of the mechanical pressure test and the modified hydrostatic test were highly correlated (r = 0.99). These methods provide more information on the barrier properties of materials that fail F 1670.