VOCs sampling

Most of Volatile Organic Compounds (VOCs) are odorous compounds. To find what chemicals to cause odour problems, VOCs sampling is sometimes needed.

There are two methods which are often used for VOCs sampling: sorbent sample tube sampling and air canister sampling.

Sorbent Sample Tubes for VOCs sampling

Sorbent sample tubes are used to collect samples of VOCs. The frequently used sorbent sample tubes include charcoal tubes, Tenax tubes and XAD2 tubes.

Sorbent tube samplling is the US NIOSH/OSHA approved method for collecting most hazardous gases and vapours from the air. When sampling, the samples are collected by opened tubes connecting to sampling pumps. Airbourne chemicals are trapped onto the surface of the sorbent when the pumps pulling sampled air through the tubes. After sampling, the tubes need to be sealed with push-on caps and freezed during the storage and transportation.

For sorbent tube sampling, sampling rate is the key factor which should be considered carefully based on the concentration level. The sampling volume is another important factor which may affect the emission calculation. Pump calibration is always needed for each sampling activity.

Canisters for VOCs sampling

Canister is designed according to US EPA methods TO-14A and TO-15, which regulate the collection, storage and analysis of VOCs using treated air sampling canister.

VOCs samples are collected into stainless steel canisters which are transported to the laboratory for analysis. Before using, the canisters need to be cleaned and pressurized with nitrogen. The canisters need also to conduct leak checking just before their on-site using. The capacities of canisters include 1L, 2L, 3L, 6L and 15L. For different purposes, the sampling rate should be well controlled.

VOCs analysis - GC-MS method