Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or a floor which slopes downward and tapers to a smaller cross-section. Contains any other recognized safety or health hazard. The focus of this article is to identify several mistakes made in evaluating and dealing with gases in permit required confined spaces. Here are a few commonly-held misconceptions that could lead to dangerous consequences. I just calibrated our gas monitor last month, It should still be accurate.
Calibration is the cornerstone of any successful gas monitoring program.
Unless you compare and adjust your instrument to a known concentration of gas prior to each use, you have no assurance of the unit's accuracy. Unfortunately they make no mention of calibration frequency. On this issue they usually refer to the manufacturer's recommendations. Be safe, contact the manufacturer of your instruments and set up your program according to their guidelines. For your protection, and the protection of your employer, always document calibrations and preserve these records in a log.