Monitoring samples taken from surfaces within the trace laboratories and trace vehicle examination bay have, with few exceptions, revealed only low levels of contamination, predominantly of RDX. Analysis of the control swabs, processed alongside the monitoring swabs, has shown that in this environment the risk of forensic sample contamination, assuming all of the relevant anticontamination procedures have been followed, is so small that it is negligible. The monitoring regime has also been valuable in assessing the process of continuous improvement, allowing sources of contamination transfer into the trace areas to be identified and eliminated. During 1989, the FEL established a weekly quality assurance testing regime in its explosives trace analysis laboratory. The purpose of the regime is to prevent the accumulation of explosives traces within the laboratory at levels that could result in the contamination of samples and controls if other precautions failed. Designated areas within the laboratory are swabbed with cotton wool swabs moistened with ethanol water mixture in equal amounts. The swabs are then extracted, cleaned, and analyzed with gas chromatographs with thermal energy analyzer detectors. 1 table, 10 figures, and 5 references