ISO 16604 Determination of Resistance of Protective Clothing Materials to Penetration by Bloodborne Pathogens Using Phi-X 174 Bacteriophage

The standard "ISO 16604 Clothing providing protection against contact with blood and body fluids - Determination of resistance of protective clothing materials to penetration by blood-borne pathogens - Test method using Phi-X 174 bacteriophage," published by the International Organization for Standardization (ISO), describes a laboratory test method for measuring the resistance of materials used in protective clothing to penetration by blood-borne pathogens. This test method uses a surrogate microbe under conditions of continuous liquid contact. Pass/fail determinations for protective clothing are based on the detection of viral penetration at a specified hydrostatic pressure using the ISO 13994 standard test device.

This test method is not always effective for testing protective clothing materials with thick inner linings that readily absorb harsh liquids. This test method involves a delicate analysis procedure. Due to the length of time required to complete this test method, it may not be suitable for use as a quality control or assurance procedure for a material or protective clothing.

Healthcare workers, in particular, who treat and care for injured or sick individuals, may be exposed to biological fluids that can transmit disease. These diseases, caused by a variety of microorganisms, can pose significant risks to life and health. This is particularly true for the blood-borne viruses that cause hepatitis (hepatitis B virus and hepatitis C virus) and acquired immune deficiency syndrome (AIDS). Because engineering controls cannot eliminate all potential exposures, care is taken to reduce the potential for direct skin contact through the use of protective clothing.

This standard pertains to protective clothing and related protective devices designed to protect against penetration by blood or body fluids. Given the diversity of healthcare environments, activities, and potential exposure to blood or body fluids, the barrier requirements for protective clothing materials vary by application. This standard describes a hydrostatic pressure test to measure the viral penetration resistance of clothing materials against a carrier virus. The selection of an appropriate test method depends on the specific application and intended use of the protective clothing. To determine the appropriate test method, a risk assessment should be conducted to determine the level of risk.

With healthcare workers, first responders, and laboratory personnel facing increasing risks from infectious diseases, the integrity of personal protective equipment is paramount. ISO 16604, an international standard that sets benchmarks for assessing the viral resistance of materials used in protective clothing, provides a rigorous laboratory method for simulating real-world exposure to viruses such as HIV, hepatitis B, and hepatitis C.

This standard addresses a critical gap in personal protective equipment performance testing by focusing on viral penetration under hydrostatic pressure. Unlike broader liquid resistance tests, it specifically targets the small threats posed by viruses, ensuring that clothing and gloves can withstand repeated contact with contaminated liquids without allowing microscopic punctures.

The principle of the described method is simple yet scientifically rigorous: a fabric sample is placed in a specialized chamber and exposed to a pressurized suspension of bacteriophages in nutrient broth, simulating body fluid dynamics. If any virus particles escape (detectable even without visible fluid leakage), the material collapses. This hydrostatic pressure setup simulates the force of blood spatter or spray, up to the pressures specified in relevant standards.

The heart of the test is the penetration test cell, which holds approximately 60 ml of test fluid and has a transparent flange for visual monitoring. Supporting equipment includes:

• A holding screen to prevent excessive deflection of flexible materials (limited to a maximum of mm).
• An air pressure source providing 20 kPa for controlled hydrostatic force.
• Precision instruments such as 0,02 mm thickness gauge, incubator (36 degrees), water bath (45 degrees) and centrifuge (10.000 g).
• Microbiological basics: sterile petri dishes, pipettes and a spectrophotometer for optical density controls.

The test mainly goes through the following steps:

• Sample preparation: Samples are cut to fit the test cell (typically 7,62 cm in diameter), and thickness and mass are measured.
• Setup of media and controls: Sterile nutrient broth, top agar, and sedimentation plates are prepared. Positive/negative controls are applied to verify bacteriophage titer.
• Compatibility check: A preliminary analysis shows that the material does not inhibit viral growth.
• Bacteriophage suspension: The virus is grown to the required titer and harvested, then loaded into the cell.
• Exposure phase: Successive pressures (e.g. 0, 1,75, 13,8, 20 kPa) are applied during curing periods, observing for leaks.
• Penetration analysis: The inner surface is rinsed with analytical fluid, diluted if necessary, and plated on E. coli lawns. Incubate at 36°C and count the plates; clear zones indicate bacteria lysed from escaped virus.
• Evaluation: Zero plaque indicates a successful outcome. Any detectable PFU/ml, even at low pressures, indicates failure.

Our organization, with its competent and experienced team, has been understanding the needs of its customers for years, providing them with the advanced testing services they need, and assisting them in the establishment, implementation, and improvement of management systems. In this context, we also provide testing services in accordance with the ISO 16604 "Clothing Providing Protection Against Contact with Blood and Body Fluids - Determination of the Resistance of Protective Clothing Materials to Penetration by Bloodborne Pathogens - Test Method Using Phi-X 174 Bacteriophage."