They're used with hand pumps that draw a sample of air into the tube. The tubes are sealed at both ends when they come out of the package. When it's time to sample, the end of the tube is broken off, and the tube is inserted into the pump.

When using colorimetric tubes the proper number of pump strokes is?

The method of the operation

Using the pump, the user must draw in the air sample through the tube to pull in the entire colored length. The number of pump strokes is indicated on the tube with a “n=” (if n=4, the user must pump 4 times before the reading).

Are colorimetric tubes accurate?

The American Industrial Hygiene Association (AIHA) in their manual, Direct-Reading Colorimetric Indicator Manual (Second Edition, 1993) makes the following statement on detector tube accuracy: The accuracy of detector tubes generally is considered to be +/-25% of the reading.