Gauges with a digital readout of up to to 1000 ppm (0.1%) can be easily obtained. It is advisable to have a sampling facility on the gauge so that the level produced can be sampled before using this method. Sampling gauges can be modified with a 10:1 reduction, so that levels up to and greater than 1% can be measured.
Gauges used by Exit are shown in Fig 6.2. The multi-gas sampling meter (RKI Eagle) enables the monitoring of carbon monoxide levels, carbon dioxide levels as well as the concentration of available oxygen. This gauge retails for over US$2000 and is primarily used as a research tool. A smaller hand-held device (TPI model 701 carbon monoxide analyser) that measures aspirated gas of up to 10,000 ppm is also shown. This useful gauge costs ~ US$600. A cheaper TPI gauge used by Exit with a modified 10:1 sampling probe (TPI model 770) costs ~US$200.
Sources of Carbon Monoxide From Commercial Gas Suppliers:
Cylinders of compressed carbon monoxide, either as the pure gas or as a mixture (eg 5% in Nitrogen) are available from scientific gas supply companies. There are no special restrictions but an account will be needed. Table 6.1 lists some available packaging for pure compressed carbon monoxide from BOC. http://www.boc.com/
Cylinders of special gas mixtures that contain lethal levels of monoxide are also used as source gases for some industrial lasers (eg 6% CO in gas used in the Rofin CO2
