ASTM F1671/F1671M-13

5.1 This test method is based on Test Method F903 for measuring resistance of chemical protective clothing materials to penetration by liquids. This test method is normally used to evaluate specimens from individual finished items of protective clothing and individual samples of materials that are candidates for items of protective clothing.

5.2 It is known that body fluids penetrating protective clothing materials are likely to carry microbiological contaminants; however, visual detection methods are not sensitive enough to detect minute amounts of liquid containing microorganisms (1,2,3).⁸ This test method uses media containing Phi-X174 Bacteriophage. The visual detection technique of this test method is supplemented with a biologically based assay capable of detecting virus under the specified test conditions.

5.3 Test Method F1670, allows the screening of protective clothing materials for resistance to penetration with synthetic blood as a challenge liquid. Test Method F1670 uses the same penetration test cell and technique, but exposes material specimens to synthetic blood with visual detection of liquid penetration. Materials passing Test Method F1670 should then be tested against bacteriophage penetration using this test method to verify performance.

5.4 This test method has been specifically designed for measuring penetration of a surrogate microbe for Hepatitis (B and C) and the Human Immunodeficiency Viruses. The surrogate, Phi-X174 Bacteriophage, used in this test method is similar to HCV in size and shape but also serves as a surrogate for HBV and HIV. Inferences about protection from other pathogens must be assessed on a case-by-case basis.

5.5 Part of the protocol in Procedure A and B in Table 1, for exposing the protective clothing material specimens to the Phi-X174 Bacteriophage challenge suspension, involves pressurization of the penetration cell to 13.8 kPa [2 psig]. This hydrostatic pressure has been documented to discriminate between protective clothing material performance and correlate with visual penetration results that are obtained with a human factors validation (4). Some studies, however, suggest that mechanical pressures exceeding 345 kPa [50 psig] can occur during actual clinical use (5, 6). Therefore, it is important to understand that this test method does not simulate all the physical stresses and pressures that might be exerted on protective clothing materials during actual use.

5.6 Medical protective clothing materials are intended to be a barrier to blood, body fluids, and other potentially infectious materials. Many factors can effect the wetting and penetration characteristics of body fluids, such as: surface tension; viscosity; and polarity of the fluids, as well as the structure and relative hydrophilicity or hydrophobicity of the materials. The surface tension range for blood and body fluids (excluding saliva) is approximately 0.042 to 0.060 N/m (7) . To help simulate the wetting characteristics of blood and body fluids, the surface tension of the Phi-X174 Bacteriophage challenge suspension is adjusted to approximate the lower end of this surface tension range. This is accomplished by adding surfactant to the Phi-X174 Bacteriophage nutrient broth. The resulting surface tension of the Phi-X174 Bacteriophage challenge suspension is approximately 0.042 ± 0.002 N/m.

5.7 Testing prior to degradation by physical, chemical, and thermal stresses which could negatively impact the performance of the protective material, could lead to a false sense of security. Additional tests should be considered that assess the impact of storage conditions and shelf life on disposable products and the impact of laundering and sterilization on reusable products. The integrity of the protective barrier may also be compromised during use by such effects as flexing and abrasion (8). Prewetting agents, such as alcohol, and contaminating agents, such as perspiration, may also compromise the integrity of the protective barrier. If these conditions are of concern, the performance of protective clothing materials should be evaluated for Phi-X174 Bacteriophage penetration following an appropriate preconditioning technique representative of the expected conditions of use.

5.8 This test method involves a sensitive assay procedure for determining protective clothing material resistance to penetration by a surrogate microbe. Because of the length of time required to complete this method, it may not be suitable for use as a material or protective clothing quality control or quality assurance procedure.

5.9 If this procedure is used for quality control or to support broad product claims concerning the viral resistant properties of materials used in protective clothing, proper statistical design and analysis of larger data sets than those specified in this test method should be performed.⁹ Examples of acceptable sampling plans can be found in MIL-STD-105, ANSI/ASQC Z1.4, and ISO 2859-1.

5.10 This test method requires a working knowledge of basic microbiological techniques (9) .