Sixty-One DELTA ONE
AIR MONITORING THE “OLD-SCHOOL” WAY — STILL RELEVANT AFTER ALL THESE YEARS Glenn Clapp CSP, EFO, CHMM, CFPS
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here is no doubt that modern technology has enhanced our air monitoring capabilities not only in the number of substances we can monitor but also in the accuracy of the air monitoring that we perform. Even though we have made amazing gains in the air monitoring that we use we should not turn our backs on some of the “tried and true” old-school methods used in the past that are sure to work for us in tight situations. By oldschool, we do not mean going back to the days of using canaries and fire damps as was done in mining operations to detect hazardous atmospheres, but rather methods such as power Hydrogen (pH) paper, oxygen sensors to determine the concentration of oxygen-displacing substances, metal oxide sensors, sulfur sticks for ammonia detection, and colorimetric tubes.
If we look back to our initial hazmat technician training we will remember that we monitor for radiological substances first and then for corrosivity after that, underscoring the need for detecting corrosive environments that can attack the meter sensors, respiratory protection, and chemical protective clothing that our very lives depend on. We can use digital pH meters to determine the corrosivity of a liquid, however, pH paper is often the most effective means of monitoring corrosive environments. pH paper is inexpensive and can be obtained in various ranges of detection that show changes in pH through color changes on the paper. We can wet pH paper down with distilled water to detect corrosive vapors as well as use it in direct contact with liquids to determine if a substance is an acid or base. We need to also lead with pH paper taped to the end of a dowel as we
enter possible hot zones and should tape pH paper to our hazmat suits (both wetted down with distilled water) to visually indicate corrosive environments. In addition to allowing us to determine the pH of a substance, pH paper also can serve as a rough estimator of vapor pressures. The further away from a substance the pH paper exhibits a color change, the higher the vapor pressure of the substance. The second old-school method of air monitoring that we will discuss is the use of an oxygen sensor for non-traditional purposes. The standard four gas meter setup includes sensors to detect carbon monoxide, hydrogen sulfide, flammability, and of course oxygen. If we encounter a substance that displaces the oxygen we can use our oxygen sensor to determine the approximate concentration of the substance. As our atmosphere contains 20.9% oxygen in the
air at sea level, we can state that oxygen comprises approximately one-fifth of air. If an oxygendisplacing substance is present in the atmosphere we can determine the difference between the oxygen sensor reading and the normal 20.9%. We then multiply the result by five as oxygen is one-fifth of the atmosphere. That result can then be converted to parts per million (ppm) through the conversion factor of one percent concentration being equal to 10,000 ppm to approximate the concentration of the oxygen-displacing substance. For example, let us say that our oxygen sensor is reading 20.8%. We subtract that value from 20.9%, yielding 0.1%. We then multiply that value by five to obtain 0.5%. Multiplying the 0.5% by 10,000 ppm (the conversion factor stated above) then lets us determine that the approximate concentration of the oxygen-displacing substance
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