A study of the stability of methanol-fueled vehicle emissions in Tedlar bags

Tedlar bags are often used to collect vehicle exhaust emissions samples. Using 60-L Tedlar bags and Fourier transform infrared (FTIR) spectroscopy, the authors have conducted a series of experiments in an effort to determine whether M85-fueled vehicle emission samples are stable over a period of time. They report here a minimum methanol and formaldehyde percent recovery after a period of 6 h of 96% and 95%, respectively. After a period of 25 h, the minimum methanol recovery was 82% and the formaldehyde recovery was 81%. To determine whether the losses observed in the methanol and formaldehyde concentrations were dramatically affected by the presence of other components in vehicle exhaust, bags containing only methanol or formaldehyde standards were examined. Over a 6-h period, the minimum methanol and formaldehyde percent recoveries were 97% and 96%, respectively. After a period of approximately 25h, the minimum amount of methanol recovered was 91%, and the minimum formaldehyde recovered was 87%. These results clearly suggest that the samples are stable in large Tedlar bags for at least 6 h