Air Sampling for Odour and VOCs

The ultimate goal of air sampling is to obtain statistically representative samples of environmental populations. There are many guidelines published by different government agencies and authorities to addresses many aspects of sample collection, handling, preparation, and shipment to minimize sample losses. The final selection of sampling protocol not only requires the understanding of the emission processes but also the knowledge of the analytical methods.

Odour and VOCs can emit from various sources: point sources, area sources, volume sources and fugitive sources. We can apply custom designed sampling equipment to determine both concentrations and emission rates: a portable wind tunnel system, isolation flux hood, sampling enclosure for open bed with outward flow and the DynaSampler for hot and wet sources.

For every sample, the sampling bag is rinsed by filling the bag with the odour sample and then squeezing the odour sample out of the bag using our custom designed odour sampling apparatus, the DynaDrum and the DynaBox.

In order to determine the emission rate, we take the temperature, humidity and air velocity readings at the source. If necessary, the predilution of the sample is performed to reduce the moisture content in the bag.

A small capacity (5 litres) and thicker (25 microns) sampling bag (Nalophan TM) is used for odour sample collection and storage. The small sample volume is likely to reduce the sample losses through the sample storage. Furthermore, the predilution of the samples using Nitrogen gas can preserve the sample for an extended period of time if transportation is required.

For VOCs sampling, we will use different sampling approaches from wet chemistry, solid absorbent, to canister on the basis of the target compounds and analytical methods. Using the DynaSampler predilution probe, we can extend our sampling capability to any hot and high strength of source.

To ensure a successful sampling program, several collocated samples for the purpose of field quality control should be taken. The exact number of samples will be dependent upon a number of factors: VOCs concentrations and moisture content levels. Therefore, a full set of quality control procedure would require up to a total of six samples.

In some cases, there are some technical challenges in the execution of sampling program. The low air flow rate passing through an absorbing tube is necessary to ensure the retention of target compounds. The high temperature and high moisture of the air sample may require the pre-treatment of the air sample. The different emission sources may also add some difficulties.

With over 28 years experience in developing sampling equipment for the determination of odour and VOCs emission from various sources, we can collect odour and VOCs samples from the following industrial and agricultural sources: