Indoor Air Quality Sensors in the Workplace

Indoor Air Quality

In this 3 part series we discuss indoor air quality monitoring (iAQM) and it’s applicability to commercial buildings. Part 1 discusses iAQM from a building occupant perspective – the basics. Part 2 will discuss the technology behind an iAQM system from a holistic and generic perspective. Part 3 will review a commercial indoor air quality monitoring device we developed for a client.

Indoor air quality monitoring (iAQM) basics

Indoor Air Quality Monitoring (iAQM) uses commercial-grade sensors to monitor the air quality inside a building to manage the comfort of the occupants and protect their health. Monitoring is performed across a wide variety of sensing parameters. As a minimum, this includes temperature and humidity. In addition, carbon dioxide (CO2) is also monitored as it’s essential in optimising productivity. Other parameters include light and noise levels. These are the obvious and easy parameters to detect to assess comfort.

The detection of volatile organic compounds (VOCs) is also important. This includes formaldehyde, benzene, ethanol and similar chemicals found in paint thinners, cleaning agents, aerosols and other man-made products. They can also be exhumed by air conditioning ducting that has aged and has insulation material in the process of breaking down, so it’s important to detect them.

Particulate matter sensors detect dust and other particles in the air – this includes smoke through bushfire ingress. The most common measurement parameters are PM2.5 and PM10, meaning particles less than 2.5um diameter and less than 10um diameter, respectively. Readings are based on micrograms per m3, thus stipulating a concentration.

Some systems measure carbon monoxide and nitrogen dioxide. However, these are not relevant in an office environment unless the office is in a shared vehicle environment such as a garage as they are emitted by motor vehicles. Barometric pressure is also not relevant, despite the fact some systems measure it.

The raw sensing data is uploaded to an analytics engine and a dashboard where it is available for viewing through a browser or a mobile app. More importantly, however, meaningful and actionable insights need to be derived. These include the need and ability to adjust air conditioning to bring in fresh air and reduce CO2 to prevent occupants from feeling sleepy and unproductive.

Identifying air conditioning operating outside of the optimum temperature and relative humidity ranges is also important as occupants will feel uncomfortable and unproductive if this requirement is not met. Noise and light levels also fall in the same category but are not usually harmful.

VOC’s and particulate matter sensing (PM2.5 and PM10) can be harmful. Therefore, these parameters need to be monitored as the health of occupants is directly affected by them. In addition, they need to be averaged over a period of time – typically 24 hours – to determine their impact on the health of the occupants. This is where analytics and algorithms are particularly important.

Many buildings are assessed for indoor air quality and comfort based on NABERS and WELL standards. Commercial grade iAQM systems cannot assess a building’s rating based on these standards, as their accuracy is not at the same level as the $30,000 scientific-grade systems used to perform these assessments. However, they can be used as a guide and particularly to baseline the building and make a comparative year on year assessment using the analytics engine that’s provided with the product. This allows the occupier to trend the health of the building and gain some insight into whether this year’s assessment will be better than last year and other years.

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