Recent FDA enforcement policy supports the use of Tenney environmental chambers for bioburden reduction on N95 respirators during the coronavirus (COVID-19) public health emergency. The use of dry heat processing to reduce the risk of transmission of the SARS-CoV-2 virus, and limited reuse of NIOSH-approved filtering face-piece respirators, were cited in the FDA guidance.

Environmental chambers such as those manufactured Tenney Environmental, a division of Thermal Product Solutions, can be customized for treating bioburden on N95 respirators, says the company. Reprogramming to the TPS bioburden reduction (BBR) cycle makes the chambers immediately available for processing respirators. Use of the company’s Dry Heat BBR process is intended to support the single-user reuse of compatible N95 respirators as a supplement to existing CDC reuse recommendations.

FDA policy states: “Based on currently available evidence, dry heat at T=75°C [167°F] for t=30 minutes should reliably achieve ≥3-log reduction in non-enveloped virus or vegetative bacteria on respirators.” This reduction level corresponds to a 99.9 percent elimination of the stated bioburdens. The policy goes on to state: “Based on currently available evidence, dry heat at T=75°C for 30 minutes should not affect the filtration efficiency, breathability, and fit of respirators.”

Microbiological testing performed for TPS LLC by an independent laboratory confirmed achievement of the minimum 3-log (99.9 percent) BBR stated in the FDA policy.