NIOSH has corrected a problem at its Pittsburgh Gas and Vapor Laboratory that was affecting gas and vapor testing for NIOSH respirator approvals. According to a February 5 letter to manufacturers, the NIOSH Safety Office had placed the Pittsburgh Gas and Vapor Laboratory on a safety stand-down due to fume hood airflow issues. All gas and vapor operations at the laboratory ceased while NIOSH worked to correct the issue.  The letter stated that an external calibration service contracted by the agency’s Safety Office determined that flow measurements of all the fume hoods in the Pittsburgh facility were higher than acceptable limits. If a release occurred during a test operation, the operators and other building occupants would be at an “unacceptable risk of exposure,” NIOSH’s letter explained.  Gas and vapor operations resumed on March 26, and NIOSH prioritized approval projects that were affected by the stand-down. Further details from NIOSH are available on the agency's website.