Detector tubes

Direct rea ding. a instmments Continuous monitors Pumps—sorbent sampler Detector tubes Passive badges... 

Various types of detector tubes have been devised. The NIOSH standard number S-311 employs a tube filled with 420—840 p.m (20/40 mesh) activated charcoal. A known volume of air is passed through the tube by either a handheld or vacuum pump. Carbon disulfide is used as the desorbing solvent and the solution is then analyzed by gc using a flame-ionization detector (88). Other adsorbents such as siUca gel and desorbents such as acetone have been employed. Passive (diffuse samplers) have also been developed. Passive samplers are useful for determining the time-weighted average (TWA) concentration of benzene vapor (89). Passive dosimeters allow permeation or diffusion-controlled mass transport across a membrane or adsorbent bed, ie, activated charcoal. The activated charcoal is removed, extracted with solvent, and analyzed by gc. Passive dosimeters with instant readout capabiUty have also been devised (85). 

Detection of Bromine Vapor. Bromine vapor in air can be monitored by using an oxidant monitor instmment that sounds an alarm when a certain level is reached. An oxidant monitor operates on an amperometric principle. The bromine oxidizes potassium iodide in solution, producing an electrical output by depolarizing one sensor electrode. Detector tubes, usefiil for determining the level of respiratory protection required, contain (9-toluidine that produces a yellow-orange stain when reacted with bromine. These tubes and sample pumps are available through safety supply companies (54). The usefiil concentration range is 0.2—30 ppm. 

Table 10.19 Selected sources of inaccuracy in use of colour detector tubes...

Other tubes (long duration detector tubes, porous polymer tubes etc.)... 

Detector tube kits generally include a hand pump that draws a known volume of air through a chemically treated tube intended to react with certain contaminants. The length of color stain resulting in the tube correlates to chemical concentration. 

Screen the sampling area using detector tubes, if appropriate. Determine the appropriate sampling technique. Prepare and calibrate the equipment and prepare the filter media. 

Detector Tubes/Pumps Detector tube pumps are portable equipment which, when used with a variety of commercially available detector tubes, are capable of measuring the concentrations of a wide variety of compounds in industrial atmospheres. Operation consists of using the pump to draw a known volume of air through a detector tube designed to measure the concentration of the substance of interest. The concentration is determined by a colorimetric change of an indicator which is present in the tube contents. 

Detector tubes/pumps are screening instruments which may be used to measure hundreds of organic and inorganic gases and vapors or for leak detection. Some aerosols can also be determined. Detector tubes of a given brand are to be used only with a pump of the same brand. 

The tubes are calibrated specifically for the same brand of pump and may give erroneous results if used with a pump of another brand. A limitation of many detector tubes is the lack of specificity. Many indicators are not highly selective and... 

Calibrate the detector tube pump for proper volume measurement at least quarterly. Simply connect the pump directly to the bubble meter with a detector mbe in-line. Use a detector mbe and pump from the same manufacturer. Wet the inside of the 100 cc bubble meter with soap solution. For volume calibration, experiment to get the soap bubble even with the zero ml mark of the buret. For piston-type pumps, pull the pump handle all the way out (full pump stroke) and note where the soap bubble stops for bellows-type pumps, compress the bellows fully for automatic pumps, program the pump to take a full pump stroke. 

Detector tubes should be refrigerated when not in use to prolong shelf life. They should not be used when cold. They should be kept at room temperature or in a shirt pocket for one hour prior to use. Lubrication of the piston pump may be required if volume error is greater than 5 %. 

Detector tube A direct method for identifying airborne contaminants, also known as length-of-stain tube. It is a convenient tool for detecting and quantifying contaminants in field or emergency situations. 

Table 9.5 Compounds for which colour detector tubes are available from one supplier...

LDDT Long-duration detector tubes PC PRO-TEK PT, Colorimetric Readout UV Ultraviolet... 

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