Infared Thermometers.. Yuck!



There are three reasons why I don’t like infrared thermometers for most HVAC tasks.

#1 – The Laser is Misleading
The laser dot is just a point of reference, not an exact point where it is reading. Often the thermometer will read lower, higher or over a MUCH wider area. Unless you are right up on what you are measuring you can’t be sure the result you are getting is correct.

#2 – They Only Read Surfaces
An infrared reads surface temp only, not air temp . This is necessarily a problem, but “shooting a vent” is not the same as measuring the air temperature coming out of it.

#3 – They Can be VERY Inaccurate
Infrared thermometers are only accurate on surface that have high “emmisivity”. These are things usually soft or porous surfaces like meat, or carpet or drywall. Metals have a low emmisity which means that if you are reading a pipe an infrared could read much lower than the correct temperature.

Infrared thermometers can be useful to do comparisons where reading the correct temperature is less important than comparing one spot to another, such as looking for hot spots in a panel, or checking a zone to see if a damper is open.

So long as you use the right tool for the job you should be fine, but in general….

I don’t like infrared thermometers.

— Bryan

P.S. – While I don’t like infrared, I REALLY like thermal imaging. Check out these nice products from FLIR –


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