MEASUREMENT OF CHLORINATED HYDROCARBONS BY PID WITH A LONG LIFE 11.7 LAMP
J. N. Driscoll, PID Analyzers, LLC

Published in the July 2008 Edition of Industrial Hygiene News

The first commercial photoionization detector (PID) was introduced in 1974 (1,2) by HNU Systems. This PID used a sealed short wavelength (121 nm/10.2 eV) UV lamp. In 1979, we introduced an 11.7 lamp in response to the need for detecting chloroalkanes for the chemical industry (VCM production) and low molecular chloroalkanes for emergency response and hazardous waste field surveys (3,4). The 9.5 and 8.3 eV lamps were developed at about the same time.
HNU developed the sealed 11.7 lamp (LiF crystal) in 1979 and extended the lifetime of the lamp from a few hundred hours to > 500 hours through the use of a unique lamp design in 1989 (5). Long term lamp storage for our 11.7 lamp has never been a serious problem. Many of our customers have had 11.7 lamps for 3-5 years. Of course, the lifetime is 600-700 operating hours due to the yellowing of the lithium fluoride crystal (from patent). The Model 102 PID warms up quickly (15 sec), so turn on the analyzer just before the measurements and turn the analyzer off as soon as the measurements are through. Some choose to use just use an 11.7 lamp because of its uniform response to VOC's. Here, the lamp typically lasts about two years. One must keep liquid water away from the 11.7 Li F window since LiF is slightly soluble in water. During operation of the analyzer, there is no effect of humidity on the response.
To continue reading, Click on the QUICK LINK on the left-hand margin labelled "Recent Article in IHN".

 Model 103 is an Analyzer that is designed for indoor air quality (IAQ) measurements It has a very fast response time, extended range from 1 ppb, elimination of any moisture sensitivity, capability of having up to 4 sensors and datalogging (see rendition). The most typical optional sensors are the IR (CO2) and % RH plus one additional EC sensor of the customer's choice