Re: Temperature Requirements for an In-House Calibration Lab
20 Deg C is a common requirement for a dimensional lab, while 23 Deg C is a common requirement for an electronic lab. What I've had to do is make a chart listing the temperature requirements for my standards and base the lab requirements for them.
If you are using gage blocks, you'll need to consider not only that they are normally certified with values at 20 Deg C (so you may have to apply correction factors if your area is different), but stability will impact settling of devices being calibrated.
In the electronic areas, you'll need to see what the maximum and minimum operating (not storage) temperatures are for each standard, and possibly some numbers for items being calibrated.
For an electronic labs also, 23 Degrees C plus or minus 5 Degrees is a typical least accurate limit, 23 +/- 3 is typical medium accuracy, and an electrical standards lab should typically be 23 +/- 1 Deg C. Dimensional labs that use gage blocks are typically 20 Degrees C +/-1 Deg C.
As for RH, my tightest requirement is 30 to 70 %RH. 45%RH +/- something (depends on your circumstances). One of the typical lower RH limits is 30%RH (as that is considered an ESD threshold).
Those are just a few examples. If it were me, I would make a manufacturer/model list of my most critical lab standards, and look up their temp and RH limits along with coefficients (where applicable), and put them in a table. This is a handy document to have around.
One other recommendation is that if possible, what ever limits are on your standards, set your lab limits a little tighter to preclude problems. As you would need to potentially shut down operations when there is an excursion outside your limits.
And a final thought is to keep a watchful eye when reading specs that some instruments have more than one set of limits. A Fluke 8508A high accuracy digital multi-meter, for example, has separate specs for different lab environments.