"Voilà pourquoi il faut utiliser un détecteur de gaz…lorsque le ... Reconnaissant ce fait, je recommande qu'un test fonctionnel (“bump” test ) ..."
http://www.sosincendie.com/sos/FR/Articles_ChristianRousseau...

"Bump Tests vs. Full Calibration

There are two methods of verifying instrument accuracy: a functional or bump test and a full calibration, each appropriate under certain conditions. A bump test verifies calibration by exposing the instrument to a known concentration of test gas. The instrument reading is compared to the actual quantity of gas present (as indicated on the cylinder). If the instrument’s response is within an acceptable tolerance range of the actual concentration, then its calibration is verified. (Note: It is recommended that users check with the detection equipment manufacturer for the acceptable tolerance ranges.) Instruments should be "zeroed" before the bump test in order to give a more accurate picture of the bump test results. When performing a bump test, the test gas concentration should be high enough to trigger the instrument alarm. "
http://www.osha.gov/dts/shib/shib050404.html