Last week I talked about some of the potential issues for Emergency Responders re build up on the Fresnel lens system in an infrared temperature gun.  Smoke & ash from fires are one set of issues, and chemical extinguishing agents are another.  Chemical vapor residues from a chemical leak (say methyl bromide, for example) can cause problems, too.  There's a fourth category for all detection & measurement equipment, but I'll address that next posting.

But how often should you clean a top notch temperature gun (say our Top Temp Gun or the Flash Point Temp Gun)?  Here's the answer from our techs:

You're looking at a Fresnel lens sysem that we use for our infrared temperature guns.  Notice the ridges along the tapering cone that lead down the barrel to the lens.

I've been hammering this theme home for a while as regards photoionization detectors, but I promised to bring it around to our infrared temperature guns and today I will,

Even though we handle 100:1 distance to spot infrared temperature guns with Class III laser sights, the situations that hazmat responders have to deal with can involve lots of smoke, dust, chemical leaks and or extinguishants.  If you're not using our Top Temp Gun, it means you'll have to be even closer.  With somebody else's infrared temp gun, say a 50:1 distance to spot ratio, you'll have to be twice as close to get a decent reading.

What is distance to spot ratio?  For a 100:1 infrared temperature gun, it means that at one hundred feet you will be measuring a circle with a 1 foot radius.  That's a tight spec.  It's a real instrument that can save lives.

But what if, during an emergency run, you use your temperature gun in a smokey environment, or while your using it, extinguisher fumes blow your way.  Or chemical fumes from a factory?

The answer is that you have to clean it, just like in the case of the PID.  Swab the ridges and the lens with isopropyl alcohol.  Most people forget to clean the ridges that lead up to the main lens.  That's a cricital mistake.  A bad mistake.  Those ridges aren't there for nothing.  They're part of the instrument's operative principle.  So clean them as often as you clean the lens.

Clean them after every emergency you take the infrared gun to.  That way you'll be sure to get more accurate readings.  How inaccurate can the readings be if the unit's lens package (including the ridges)isn't cleaned?

I'll fill you in on that next time.

There has been some controversy over the impact that humidity has on their readings, with one company- Ion Science- claiming that humidity variations have a significant effect on detection suppression.  In high humidity environments that claim this suppression could be in excess of 50%, which makes humidity and serious consideration when trying to get an accurate reading out of a PID.  However, there are rumors of a new study showing that improvements in PID technology have knocked that down to the range of only 10%.

Of more concern to me is the effect of smoke on PID readings at the time of an emergency event and residual contamination on the detector cell because of the smoke and/or chemical extinguisher vapors.  In earlier postings I have stressed the importance of cleaning PID cells after a chemical event.  Now I raise the question of how much smoke or other particulate and/or condensate fumes have on the accuracy of a PID's readout.

To my knowledge, there have been no studies conducted on this issue by any of the gas detection companies or sensor manufactuerers.  I'm going to keep pushing them to look at this problem, and hope you'll push for the same.  This problem shouldn't be ignored.  After all, the responders actually are at risk in the field.  Gas detector salesman typically don't tend to show up at emergency events where toxic gases are involved.