Swedish car dealership compares air quality indoor and outdoor with AQMesh

Two AQMesh pods were used to measure NO, NO2, O3 and CO during May and June 2017 at one of the largest car dealerships in Stockholm, Sweden, located on the highway between Stockholm city centre and Arlanda airport. The objective was to measure the air quality outside and inside the combined showroom and workshop, demonstrating the importance of measuring common traffic-related pollutants indoors as well as outdoors. The project was also to assess the suitability of AQMesh for this application, including ease of installation and relocation.

The air in the building is managed using a standard heating and ventilation management system which ensures adequate air exchange when the building is in operation.

Analysis of the readings shows that the AQMesh pods presented very similar results when both pods were located outdoors together, on the roof, for several weeks before 9th May. Comparison of the two pods for NO2 gave an R2 of 0.94 and both pods showed very similar peaks, particularly in NO, as a result from traffic on the highway. It is important to show that two co-located units read near-identically if any conclusions are to be drawn from differences in readings when the units are used to measure in different locations.

One of the pods was moved indoors between 9th May and 9th June – this can be clearly seen in the temperature plot comparison for both pods during May and June. The indoor unit showed significantly elevated levels of NO and CO indoors during that time, compared to the unit which remained outside. Although the NO levels indoors largely tracked the outdoor levels, they were consistently around 40-50ppb higher. This may be because the ventilation system is not adequately exchanging air indoors, as the ventilation system in the building is activated at 7am and stops at 6pm when the premises close.

The pods were mounted together outdoors again at the end of the indoor trial, clearly showing that the units continued to agree with each other when measuring in the same space, with a pod-to-pod R2 of over 0.8.

Whilst many heating, ventilation and air conditioning (HVAC) systems focus on CO2 measurement and particle filtration, they can actually make levels of common pollution gases, such as NO2, worse. Air intakes may be situated where outdoor air quality is poor, such as in a car park or near a road, air intake is often during busy traffic periods, and HVAC systems may be switched off just as outdoor air is clearing, trapping pollution indoors overnight.

With diesel exhaust fumes now classified as a class 1 carcinogen, forward-thinking companies are becoming the first to understand these issues and are focusing on management of indoor air to ensure that the air quality for their workers is at least better than outdoors. AQMesh can also quantify exposure of employees to NO2 and other pollutants when working outdoors, such as on civil engineering sites, directing traffic, or driving a bus.

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