Posted By Frank Hallett Hi S? It depends entirely what you need it for, how it's going to be used and the competence of the person using it. What do you mean by "general condition testing"? Frank Hallett

Posted By S.Alder Sorry , should have been more descriptive. Basically i just want to conduct local atmospheric testing on some of our production processes. I already have environmental monitoring performed by an external company on a bi annual basis. This is the tube based system and i just want to be able to check the existing control measures on a quarterly basis to make sure everything is ok. i personally think the system must be pretty good as the external provider uses a gastec for some testing. I was just looking for feedback from anyone else familiar with this piece of kit. Shane

Posted By Fred Pratley Shane, depending on what you are testing for, there is a whole range of passive badge systems where all you do is get people to wear the badge for a given time. This gives a better idea of exposures than either the Gastec or dreagar tube system, both of which are simple to use, but are only intended to give a snapshot at the time of testing. Presuming that you are maintaining control of exposures using some form of extraction, I find it far better to spend money on things that confirm your extraction kit is working as well as it was on the day your outside people tested. you then only have to watch for changes in the way the process is operated. However, I'm curious to know what makes you feel you need to increase testing intervals. Regards Fred

Posted By Stephen D. Clarke Hi, I've used both Gastec and Draeger in the past nothing really to choose between them both give a quick snapshot of the concentration. When I've used them it has been to see if I have a problem. Typically I would define that as any concentration greater than quarter of the WEL but it will of course depend upon the toxicity and health effects of the substance you are measuring. It is as well to remember that these devices are not very accurate I think something like 25-30% accuracy also its only a spot check so air movements, convection currents etc could easily give a unrepresentative result, you'll probably need to use several tubes to get an true idea of precision. Accuracy figures are often quoted with the tube leaflet as are interferences from other chemical vapours. I think you also need to allow for differences in air pressure and temperature. A bit of chemical knowledge will help to make a sensible judgement on chemical interferences which could alter the reading up or down. If a problem is identified then more accurate measurement will be needed with for example absorption tubes with subsequent gc or gc/ms.