042 -- The Effect of Air Sampling Tube Material on Ozone Measurements

Ozone is a highly toxic reactive gas that has an increasing application in wide industrial and environmental operations. The exposure limits of ozone for workplaces are low as commonly in 100 ppb or less; therefore, accurate measurement of ozone concentration in workplaces is crucial for protecting workers’ health and safety. Ozone can be readily decomposed within the sampling tube due to chemical reactions with the tube’s inner surface or other contaminants inside the tube. The tube material should be resistant to ozone and, more importantly, inert to ozone reaction. PTFE, FEP, and austenitic stainless steel are suggested to use for ozone sampling. Besides, silicone and Viton—common soft tubing materials—are known to be ozone-compatible. This paper tested eight different tubing materials—PTFE, FEP, stainless steel 316, stainless steel 304, Viton, Silicone, Tygon PVC, and FEP lined Tygon PVC (Tygon SE200)—to investigate how they affect the ozone measurements. We monitored the ozone concentration from the inlet and the outlet of each line for 1 h. At 100 ppb of ozone, the ratios of the outlet ozone concentration to the inlet are measured between 0.27 and 1.0. The effects of ozone concentration and humidity are also investigated. Except for PTFE, FEP, and Tygon SE200, the rest of the tested tubing materials showed reductions in the ozone monitor readings, causing false assurance of ozone exposure.