An emerging class of personal air quality monitoring devices fills a need for people who care about pollution exposure in their immediate vicinity. This level of granularity does make a difference, it seems. Envirotec spoke to Rainer Kiirsk, who helped develop the AirSniffler, a seemingly ground-breaking product for its power consumption and sub- 70 price tag, as well as the usefulness of the software that runs alongside it.
The case for personal monitoring devices of this kind seems to rest upon the realisation that air quality can vary quite noticeably over even small distances. “There are places where even 20 metres can make a difference”, says Kiirsk.
With the decision to inform ourselves about pollutant levels in our vicinity comes the opportunity to make judicious health choices – in practice, deciding to stand some distance away from a bus stop rather than directly at it might mean the difference between receiving a whole day’s recommended dosage of NOx vs 50% of a daily dosage.
Because it’s mobile and battery operated, you can walk around and start figuring out the hotspots on your own, says Kiirsk. If you’re walking near a busy road, for example, you’ll be able to see the gradient increasing as you move towards the road itself, and decreasing as you move away.
The reliability of gas monitoring equipment varies widely, and accuracy does clearly come at a price, which extends all the way up to mass spectrometry and picogram-level precision for thousands of pounds. Handheld devices like AirSniffler have to make compromises.
The device typically operates for 2-3 weeks from a 400mAh battery, with 7 weeks being the longest it can run. “There’s not much gas sensing that can take so litle energy and still operate,” Kiirsk notes. And the device also has a USB charging port.
The on-board hardware includes relatively simple MEMS semiconductor sensors, of a kind that have been developed principally for the detection of pollution from automobile exhausts.
These work by sensing a change in resistance in the air, and have separate sensing elements for oxidising gases (like NO2 and ozone) and reducing gases (CO, VOCs, and OH-group gases).
Ozone and NOx seem to present the greatest danger to human health, suggests Kiirsk. These are the ones you can’t smell – or, at least, as soon as you can, you know the levels are way beyond what is safe for humans.
Some of the most useful functionality seems to come from the software and the way the data can be interpreted – this generally runs at an app-level on a smartphone, connecting to the AirSniffler via Bluetooth. Features includes the ability to overlay geographical and air pollution data on a map, so users can gain a sense of the pollution levels in different places.
The device has been pre-set with data from WHO guidelines, in relation to safe thresholds of exposure for different gases, and incorporates a colour-based warning system, which ascends in the order of green, amber, red and black. The device also has an LED and can be set so it will flash if safe levels are exceeded.
Proprietary software is also used to provide the temperture and humidity compensation required to minimise the sensor drift that might otherwise occur.
Weighing in at 24g, AirSniffler is compatible with Android and iOS devices, and available in green and orange.