Using Detector Tubes

October 16, 2012 Dave Weber No Comments


Detector tubes (colorimetric indicator tubes) are often the first step in determining the degree of risk a hazardous airborne contaminant poses.  They are relatively inexpensive,  you don’t need any special training or qualifications to use them,  and the results are immediate.   Detector tubes help to determine if you need an Industrial Hygienist to do more sophisticated air sampling (NIOSH standard methods, direct reading instruments, etc.). 

As the only OSHA Industrial Hygienist in an area office with eight Safety and Construction CSHO’s,  I was sometimes asked “when should a CSHO make a referral to an Industrial Hygienist for more in-depth air sampling?”   My answer was – if the CSHO tested with a detector tube and the level detected was over half of the Permissible Exposure Level (PEL) a referral to a qualified (or certified) Industrial Hygienist was needed. 

The manufacturers of detector tubes give a percentage (plus or minus) for accuracy on each tube they make.  To my surprise, I have found that some tubes are more accurate than the manufacturers stated;  however, it is best to apply their accuracy numbers to your results. 

I remember one instance where I was on an inspection regarding Methyl Chloroform exposures.  I had used a detector tube for the initial sampling and the levels I measured were 65 parts per million (ppm).  Because the task  lasted for only two hours, I determined that further sampling was not required.  

A few weeks after doing this Methyl Chloroform detector tube test, the Regional OSHA Office audited this file and I was written up for not sampling for a full shift (8-hours)!  

Not long after the regional audit, I received another employee complaint from this same facility concerning a possible overexposure to Methyl Chloroform.   I  went back to this employer and this time conducted an 8-hour, full shift test for Methyl Chloroform.   The full shift test sample measured 61 ppm,  very near the 65 ppm found earlier with the detector tubes!   Shortly after that, OSHA changed their internal air testing protocol and said that Industrial Hygienists could use their “professional judgment” to determine the most appropriate method for air sampling.

Please remember that when you do use detector tubes, be sure to record the date, time and affected employees, because this information is considered by OSHA to be “exposure records”. 

In many instances, I  highly recommend the use of detector tubes because they are quick, accurate and cost effective.  If you would like to try out a Dräger Pump and detector tubes before purchasing them – they can be rented here.


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