(3) When sampling gas/vapor contaminants, it is possible to use direct
reading devices that do not require subsequent laboratory analysis. One such device is
the detector tube (see Figure 2-6), which is accurate to plus or minus 25 physical
principles (e.g., heat of oxidation and wavelength of light) to obtain direct indications of
the concentration of contaminant. These are limited to use with certain specific
contaminants. Examples of this kind of instrument are carbon monoxide monitor (see
Figures 2-7 and 2-8).
Figure 2-6. Precision piston gas detector system (A); cut away view of automatic
precision hand pump (B); bellows pump with detector tube and
stroke counter (C); and cut away view of bellows pump (D).