FDA Policy Supports the Use of Tenney Environmental Chambers to Process N95 Respirators

Posted: May 03, 2021

tenney t2 chamberTenney Environmental, a division of Thermal Product Solutions (TPS, LLC), is pleased to announce that the 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 FDA guidance document [1] supports the use of Dry Heat processing to reduce the risk of transmission of the SARS-CoV-2 virus and support limited reuse of NIOSH approved Filtering Facepiece Respirators. 

The FDA policy states that “Based on currently available evidence, dry heat at T = 75 °C 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% elimination of the stated bioburdens.  The policy goes on to state that “Based onmasks in Tenney chamber 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%) bioburden reduction (BBR) stated in the FDA policy.  In addition, samples of the processed respirators were sent to NIOSH, where they were independently evaluated.  The NIOSH test reports confirmed that the N95 filtration efficiency and fit testing scores were not significantly affected after 10 cycles of Dry Heat processing.

Numerous models of Tenney environmental chambers can be quickly reprogrammed to run the TPS BBR Cycle, making the systems immediately available for processing respirators.  Use of the TPS Dry Heat BBR process is intended to support the single-user reuse of compatible N95 respirators, as a supplement to existing CDC reuse recommendations.

“Our experienced team looks for innovative solutions to real world problems. The PPE sterilized maskshortage during the pandemic pushed us to develop a program that could effectively reduce the BBR in N95 masks to support reuse. The recent FDA policy supporting the use of dry heat systems in the processing of N95 masks allows us to supply equipment in the fight against COVID-19.”

Jeff Comitz



[1]  https://www.fda.gov/regulatory-information/search-fda-guidance-documents/enforcement-policy-bioburden-reduction-systems-using-dry-heat-support-single-user-reuse-certain