Indoor air quality

People today, whether at work or at home, tend to spend a relatively long time indoors. Consequently, the impact of indoor air quality on people’s health, comfort and work performance is all the more significant.

Indoor environments often contain hundreds or even thousands of volatile organic compounds (VOCs), the majority of which originate from the off-gassing of building materials, the use of chemicals, emissions from industrial processes, and various domestic activities such as cooking and cleaning.

Due to the large surface area of indoor walls, the enclosed nature of buildings or poor ventilation, VOCs can easily accumulate and contaminate the working environment, thereby harming people’s health.

Real-time monitoring of VOC fluctuations in indoor environments is particularly important for assessing and controlling the potential risk levels associated with exposure to indoor air pollution. At the same time, monitoring the types and sources of pollutants provides a data foundation for improving indoor air quality.

However, the chemical reactions of these compounds and the potential chemical changes that may occur between them are complex, making it difficult to analyse and evaluate them accurately.

For the real-time monitoring of indoor VOCs, rapid, sensitive and reliable analytical instruments are capable of simultaneously detecting hundreds of VOCs in the air at the ppb level. High-resolution TOF mass spectrometers and a variety of highly selective soft ionisation modes enable the precise identification and characterisation of the detected species.

Samples are introduced directly during monitoring, eliminating the need for sample preparation. This saves time and effort compared to offline GC-MS analysis, whilst also avoiding errors that may arise during sample collection and pre-treatment.

The ProC-TOF-MS online mass spectrometer is primarily used to detect and monitor the following parameters:

Indoor air VOC detection and monitoring

Common household products (such as air fresheners), building materials, furniture, materials used in the construction of car or aircraft cabins, and many chemicals used in our daily lives emit VOCs. Some of these have an odour that we perceive as unpleasant, whilst others are imperceptible to the human nose.

Indoor air pollution is often more severe than outdoor pollution. VOC exposure levels vary depending on air volume and its exchange rate, room ventilation, and outdoor air concentrations. These levels typically range from below pptv; different materials have specific VOC emission rates that must be taken into account.

Most VOCs associated with indoor air quality can be detected using ProC-TOF-MS (with a detection limit as low as 1 ppb), such as benzene, toluene, xylene and many other harmful substances that affect health or are perceived as malodours.

Cabin Monitoring – Ozone-Induced Reactions

In aircraft cabins, interactions between ozone and skin oils can produce chemical by-products that may contribute to nasal irritation, headaches, dry eyes and lips, and other common complaints among air travellers. Among the measured VOCs, nonanal and decanal are a pair of aldehydes associated with headaches, nasal irritation and other symptoms of ‘sick building syndrome’.

Impact of VOCs Emitted from LCD Screens on Indoor Air Quality

In homes and offices, a wide variety of VOCs are emitted from LCD screens in computers and televisions, including alkenes, cycloalkenes, amides, organic acids and naphthenes, which are closely associated with liquid crystal monomers. The emission coefficients of these VOCs show a significant positive correlation with ambient atmospheric humidity. Under conditions of inadequate indoor ventilation, LCD screens account for 5–20 per cent of the total volume of certain VOCs in indoor air.

Due to variations in type and quality, materials may release toxic or odourous chemicals, or both. Even at very low concentrations, these volatile gases may have potential adverse effects on production safety and product quality during the manufacturing process.

Synthetic leather in vehicles

With regard to the testing of such materials, in addition to ketones, aldehydes, aromatic hydrocarbons and amines, PU materials may also release dimethylformamide (DMF) remaining from the production process. Long-term exposure to environments containing these compounds can lead to the production of toxic secondary metabolites in the human body and cause potential liver damage.

Traditional analytical methods typically require 10–30 minutes for the injection and analysis of a single sample, whereas the ProC-TOF online mass spectrometer can qualitatively and quantitatively analyse multiple harmful substances with a time resolution of seconds.

Common VOCs, such as acrolein, acetaldehyde or acetone, are identified by their precise mass, and the differences in concentration between samples are very distinct.

Standard analytical methods generally involve the use of gas chromatography–mass spectrometry (GC-MS) to analyse gas samples collected in sorption tubes: this approach is typically time-consuming and labour-intensive, requires reference materials for qualitative and quantitative analysis, exhibits poor selectivity for odour-causing molecules containing oxygen or other heteroatoms, and is difficult to compare with studies using other methods.

The ProC-TOF automated sample-injection online mass spectrometry system can be readily applied to long-term indoor VOC monitoring. Its high-throughput, rapid sampling and analysis, coupled with reliable qualitative and quantitative capabilities, make it an ideal analytical platform for sample quality control, rapid screening of characteristic materials, providing rapid feedback on VOC emission levels during research and development, and revealing how the release of volatile hazardous substances from materials varies with external conditions.