Homeland Security Research

Research Highlights

Determining the Impacts of Decontamination Technologies on Building Materials

EPA, in collaboration with the U.S. Army Edgewood Chemical and Biological Center (ECBC), investigated decontamination technologies for restoring public buildings to a usable state after a terrorist contamination event. In the context of decontamination, contaminants of interest are those that can persist on indoor surfaces and can lead to a continuing chance of exposure long after the contamination event occurs. Testing of decontamination technologies generates objective performance data so building and facility managers, first responders, groups responsible for building decontamination, and other technology buyers and users can make informed purchase and application decisions.

Both vaporized hydrogen peroxide (VHP^®) and chlorine dioxide (ClO₂) are decontamination technologies that have been used to decontaminate indoor surfaces contaminated with anthrax and that show potential for use in decontaminating indoor surfaces contaminated by chemical agents. Building interiors may contain large surfaces composed of complex materials; therefore, testing has been performed to determine the degree to which building materials were affected by decontamination using VHP^® and ClO₂. Building interior materials used for testing were a subset of the variety of structural, decorative, and functional materials common to commercial office buildings regardless of architectural style and age.

Investigation Process

Coupons were prepared from a large enough quantity of material that multiple test samples could have uniform characteristics (e.g., test coupons were all cut from the interior rather than the edge of a large piece of material). The following materials were tested:

• Structural wood
• Latex-painted gypsum wallboard
• Concrete cinder block
• Carpet
• Painted structural steel
• Acoustical suspension ceiling tile
• Electrical circuit breaker materials (e.g., intact circuit breakers
  and component metals aluminum, copper, and steel)

The coupons were measured and visually inspected prior to testing to ensure that they were within the acceptable tolerances and were not defective and/or damaged. The testing consisted of:

• Coupon exposure: Coupons, placed within an exposure chamber having a regulated relative humidity and temperature, were exposed to the decontaminant (hydrogen peroxide [H₂ O₂ ] or ClO₂ ) for a period of time at the target fumigant concentration. Following the decontamination phase (exposure period), aeration of the chamber occurred.
  • VHP^® :  Fumigation at (i) 250 ppmv H₂ O₂ for 4 hours or (ii) 125 ppmv H₂ O₂ for 8 hours at 30°C and a starting relative humidity of <30%.
  • ClO₂ :  Fumigation at (i) 2000 ppmv ClO₂ for 6 hours or (ii) 1000 ppmv ClO₂ for 12 hours at 23.8°C and 75% relative humidity.

• Visual inspection: Coupons were visually inspected and digitally photographed upon removal from the chamber. Visual inspection of the coupon surfaces was conducted through side-by-side comparison of the decontaminated test surface and fresh coupons of the same test material (i.e., unexposed coupons). The testing staff looked for changes such as discoloration, blistering, warping, and peeling on the exposed coupons.
• Coupon aging: Coupons were aged for a minimum of 90 days following exposure to the decontaminant and then placed in open containers and stored under ambient conditions. Open containers allow coupons to age in conditions mimicking the real world.
• Data review and technical systems audits: Data generated from the testing were peer reviewed and several audits were conducted over the course of the testing to ensure data integrity.
• Physical testing: The Instron model 5582 was used for the physical property testing (e.g., tensile, compression, shear, peel, and flexural tests).
• Statistical analysis: Statistical tests were performed to determine whether the differences observed among the various test sets were merely the result of random variations in the test data or represented actual differences in the performance of the materials as a result of exposure to the decontaminants. Outliers were identified using the Dixon’s Q-Test, and statistical differences were demonstrated using the Welch’s T-Test.

Investigation Results

Testing indicated that building material coupons exposed to VHP^® or ClO₂ under the respective test conditions showed no change in appearance compared to control coupons that were not exposed to the decontamination cycles. Physical test results for the fumigated coupons showed minor changes in integrity for some materials when compared to the control coupons. The following table provides a brief summary of the results:

Table 2. Summary of Results

Building Material	Effects of ClO2 Decontaminant	Effects of VHP® Decontaminant
Structural wood	Exposure reduces tensile strength, causing furring strips to fail more rapidly.	No statistical difference (NSD) between exposed and unexposed samples.
Latex-painted gypsum wallboard	NSD between exposed and unexposed samples regarding resistance to penetration by a nail.	Exposure makes samples more resistant to penetration by a nail.
Concrete cinder block	No differences exhibited no evidence to indicate that exposure affects material.	No differences exhibited; no evidence to indicate that exposure affects material.
Carpet	Exposure slightly increases the force required to pull the carpet tuft bind.	Exposure slightly increases the force required to pull the carpet tuft bind.
Painted structural steel	No change in the maximum load required to break samples. Samples were above the ASTM- specified tensile strength requirements (by 20% or more). Exposure yields no obvious change in failure.	Exposure yields minor decreases (1–3%) in tensile strength. Samples were above the ASTM- specified tensile strength requirements (by 20% or more). Exposure yields no obvious change in failure.
Acoustical suspension ceiling tile	NSD between exposed and unexposed samples regarding the required breaking force.	Exposure causes a slight increase in required breaking force.
Electrical breaker materials	Exposure yields conflicting information. 60-amp circuit breakers showed NSD with respect to the time to trip. 30-amp exposed circuit breakers tripped more slowly than unexposed breakers.	Exposure yields conflicting information. 60-amp exposed circuit breakers tripped more rapidly than unexposed breakers. 30-amp exposed circuit breakers tripped more slowly than unexposed breakers.

See Also
Effects of Vapor-Based Decontamination Systems on Selected Building Interior Materials: Chlorine Dioxide (EPA/600/R-08/054)
Effects of Vapor-Based Decontamination Systems on Selected Building Interior Materials: Vaporized Hydrogen Peroxide (EPA/600/R-08/074)