Measuring indoor air pollution

Chinese scientists have developed a passive sampler that can be used for monitoring common indoor air pollutants. Air quality is currently an important topic in China, with air pollution rivalling food safety and clean drinking water as a key theme for Chinese lawmakers. The quality of indoor air can be just as compromised as the outside. Nowadays, people spend a large amount of their time indoors so it is important to be able to accurately measure indoor air quality.

The Tsinghua Passive Diffusive Sampler (THPDS), made by Yinping Zhang and colleagues at Tsinghua University, China, is a low-cost, passive air sampler that can be used to monitor levels of the volatile organic compounds (VOC), benzene, toluene and xylene (BTX). ‘Rapid urbanisation in China has resulted in serious indoor BTX pollution in the past few decades. However, there is little quantitative information on indoor BTX exposure and corresponding health risks in China, primarily because there has been a lack of cheap and accurate passive samplers,’ says Zhang.

Passive sampling techniques are preferred over active ones, as they are low-cost, do not require a power supply and can be left for long-term, large-scale sampling. Zhang used hydrophobic silica zeolites as adsorbents in the samplers as they have a large capacity for adsorbing BTX and are compatible with thermal desorption, the method used to transfer the samples from the sampler to the gas chromatography-mass spectrometry machine.

The THPDS was evaluated with respect to various environmental factors such as wind, temperature and humidity and found to be comparable to currently used active samplers.

‘New passive samplers using hydrophobic zeolite materials have a wide range of applications in indoor air science studies and this low-cost solution will have a great impact on VOC sampling,’ says Christopher Chao, an expert in environmental engineering and air quality at The Hong Kong University of Science and Technology.

Next, the team intend to use the THPDS in a national testing program involving 10 Chinese cities. They are also working to improve the reproducibility, storage and transportation of the samplers.