A former (sort of) client has suffered a serious event simply because they failed to follow the direct reading instrument manufacturer’s WARNINGS. The space being monitored involved NH3. The facility was using the WRONG PUMP and WRONG SAMPLING TUBE!
(emphasis by me, and I have removed the brand name from the post)
WARNING: Do NOT use the XXXXXX Slide-on Pump (VSP) when testing for target gases susceptible to absorption. Use ONLY the XXXXXXPro Pump Module for this purpose. Examples of absorbable gases include but are not limited to Chlorine (CL2) and Ammonia (NH3). Failure to follow this guideline could result in inaccurate gas readings.
and
When sampling with a motorized pump and sampling line, XXXXXXXXXXXX recommends the following:
- Never operate a pump without an internal filter installed.
- Choose the tubing type based on the target gases. If the target gases are known, use Teflon-lined tubing when sampling for these gases: chlorine (Cl2), chlorine dioxide (ClO2), hydrogen chloride (HCl), and volatile organic compounds (VOCs). For other known target gases, urethane tubing or Teflon-lined tubing may be used. When the target gases are unknown, use Teflon-lined tubing.
- Know the length of the sample line as it is a factor in determining sampling time. Sample-line length is defined as the distance from the dust filter–water stop opening to the point where the line connects to the pump’s inlet. Ensure sample-line length does not exceed the pump’s maximum draw.
Based on sample-line length, calculate the minimum time recommended for the air sample to reach the instrument’s sensors. As shown below, use a base time of 2 minutes, and add 2 seconds for each 30 cm (1 ‘) of line length. Watch the display screen for gas readings and, if present, allow them to stabilize to determine the reading.