The investigators measured the hydrogen peroxide concentration inside a sterilizer immediately after the end of the cycle, when people would be reaching in to remove the load, and found very high concentrations (34 ppm Sterrad 100S; 60 ppm Sterrad 200; and 13 ppm V-Pro1) in some cases close to the NIOSH Immediately Dangerous to Life and Health value of 75 ppm. Since the time to unload a sterilizer is fairly short, a single exposure will probably not exceed the OSHA PEL of 1 ppm calculated as a time weighted average over 8 hours, but it would probably exceed the 3 ppm 15 minute short term exposure limit found in some states (Washington and Hawaii) and even the OSHA PEL may be reached in a busy facility for someone running multiple loads a day.
ChemDAQ has received many reports from users of hydrogen peroxide emissions when the sterilizer door is opened at the end of a cycle. In a typical ChemDAQ installation the sensor is placed on top of the sterilizer and so the concentration measured will be much lower than would measured from a sensor placed inside the sterilizer chamber because the vapor gets diluted by the time it reaches the sensor.
Users often see small increases in hydrogen peroxide concentration, usually less than 1 ppm, though one model of sterilizer was found to emit much higher concentrations (~30 ppm) each time the door was opened. In this case, the hospital had four sterilizers, all new, all showing the same behavior. The manufacturer was unable to solve the problem and the hospital now instructs their technicians to open the sterilizer door at the end of the cycle and leave the area until the ChemDAQ monitor shows that it is safe to return.
Rika Yoshida, Hiroyoshi Kobayashi began their investigation in response to complaints of eye and respiratory system irritation from healthcare workers using hydrogen peroxide sterilizers. There are many similar reports of eye and respiratory system irritation from hydrogen peroxide sterilizers in the FDA’s MAUDE database and so it is likely that the results reported in their paper are not unique.
For many years ChemDAQ has been pointing out that all sterilant chemicals are potentially hazardous since they are designed to kill all microorganisms and therefore we recommend that all sterilant gases and vapors should be monitored.