Passive Air Sampling for Volatile Organic Compounds
Apr. 22 2019
Canadian federal regulation dictates the limits of carcinogenic substances, such as benzene and 1,3-butadiene, being released into the environment. Operators of petroleum and petrochemical facilities are thereby required to take measures to reduce leaks from equipment components such as valves, pumps and connectors, as well as other potential sources. These measures enable them to maintain safe exposure levels to potentially harmful volatile organic compounds (VOCs).
The principle health concern arising directly from atmospheric VOCs is from long term exposure to low levels of known and potential carcinogens. One of these carcinogens, a non-threshold toxicant that can cause harmful effects at any level of exposure, is Benzene. The Alberta Ambient Air Quality Guidelines has set a limit of 30 μg/m3 for one-hour benzene concentrations. This Canada-wide Standard will reduce our exposure to benzene.
Most VOCs contribute, in varying degrees, to the net production of tropospheric ozone by effectively interfering with the equilibrium. Such VOCs produce peroxy radicals photochemically in the presence of sunlight. In turn, these oxidize nitric oxide to nitrogen dioxide, resulting in a net production of ozone. Long term exposure is known to damage vegetation and materials.
Because of their role in ozone formation, VOCs are contributors to global warming, and have been subject to the 1992 Climate Change Convention and the Kyoto summit agreements.
When a source of VOCs is accurately identified, it allows for more effective site maintenance programs. This can generate a significant financial benefit through reducing the loss of valuable refined species. For example, pinpointing a VOC emission location, a refinery in Sweden was able to reduce their VOC emissions and save an estimated one million dollars per annum.
Working with Bureau Veritas
Our Passive Air Monitoring group in Edmonton is proficient with analytical method EPA325B. This method is used to analyze VOCs and carcinogenic substances outlined in Canadian federal regulation.
Sample collection is required every 14 days from April to December, using a thermal desorption tube. These samples are analyzed to determine the concentration of benzene and 1,3-butadiene, as well as the total concentration of all retainable VOCs.
Using gas chromatography-mass spectrometry (GC-MS) analysis for the majority of our passive air projects, we are able to deliver the industry-leading detection limits, shown in Table 1. These limits are much lower than current regulatory requirements.
In addition to VOC analysis, Bureau Veritas’ passive air laboratory offers the convenience of expert consulting and the analysis of six additional pollutants: SO2, H2S, NO2, O3, NOx and NH3.
Table 1: Target Compounds with Minimum Detection Units
|TARGET COMPOUNDS||MDL, μg/m3|
Our Test Method
The Bureau Veritas test method involves exposing a thermal desorption tube outdoors for 2 weeks under our protective rain shelter. After exposure, the tubes are then thermally desorbed and analyzed.
Pre-conditioning of the TD tubes is a critical process to ensure precise and accurate results. Our laboratory teams have dedicated trained staff to execute proper pre-conditioning. Tubes must be used within 30 days of being prepared and batched sets of matched lab blanks, field blanks and duplicates are required to be transported together. New pre-conditioned batches should be sent out on a two-week schedule.