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Monitoring air quality with PACMAN


NIWA has developed a new device for measuring and monitoring indoor air quality: PACMAN. The tool will help scientists understand the sources of pollutants to which people are exposed indoors – a place which may, for some people, be more dangerous for their health than outdoors.

The problem

In New Zealand, poor air quality is estimated to cause 1175 premature deaths and cost over $4 billion each year. Poor air quality can damage both our cardiovascular and respiratory systems. Different types of pollutants have different effects on our health.

So far, most research into air quality has focused on the outdoors, but we spend about 80% of our time indoors, so it is important that we gain a better understanding of the pollutants to which people are exposed indoors. Also, recent research indicates that exposure to pollutants can be much higher indoors than outdoors.

We want to identify which activities control the concentrations and exposure of pollutants to people in their homes so that we can answer questions like:

  • can one ten minute cooking session expose people to high levels of pollution?
  • how does that compare to the starting of a woodburner or to second-hand smoking?
  • are there other activities that contribute to the indoor dose of pollution, such as incense burning, solvent evaporation, dusting?
  • are we safe indoors from the pollution outside?
  • is it preferable to live in a well-sealed home or a well-ventilated one if the sources of pollution are within our homes?

The solution

We have developed the open source Particles, Activity and Context Monitoring Autonomous Node – PACMAN for short.

PACMAN is a small box containing sensors which allow it to measure carbon dioxide, temperature and airborne particle concentrations. It also contains motion and distance sensors which allow it to track the movements of people, enabling it to identify which kinds of activities affect air quality.

In order to be deployed to large numbers of homes, it was designed from off-the-shelf components to make it cost-effective to build and run. In its simplest form a PACMAN could cost as little as NZ$300 to build (only CO2, temperature and dust, without distance sensor or wireless communications) while a fully fledged one (including CO and distance sensors as well as a wireless modem) costs around NZ$500. Also, even a novice electronics enthusiast should be able to put one together in about one day.

Learning which activities lead to higher emissions indoor and how these pollutants mix and interact with each other in homes – all of which have different atmospheres inside depending on how people are living in and using their indoor spaces – will eventually lead to healthier homes.

We have developed PACMAN as part of an international community involved in the open source development of instruments and software for recording indoor air quality. The community consists of both participants and researchers, who work together to share ideas and resources.

As PACMAN is an open source project, you can build your own. The hardware design files are licensed under the Creative Commons Attribution Share-Alike license, while the firmware code is released under the GNU Lesser General Public License


PACMAN has undergone several laboratory tests and been tested in a small number of Auckland, Wellington and Christchurch homes since 2011 , as well as homes in Ulan Bator, Mongolia and in British Columbia, Canada.

The instruments were exposed to cooking, toasting, smoking and other smoke sources in a controlled experiment, and during normal occupation of the house.

A short series of controlled tests were performed, which confirmed that PACMAN can distinguish between indoor and outdoor sources of pollutants, and even discriminate between different indoor sources. The PACMAN's readings were also consistent with the readings of much more expensive instruments.

The combination of CO2 and movement data was able to indicate the presence of persons in the room, although there was some ambiguity in the readings. We are conducting trials to see whether it matters where in the home the PACMAN is placed. The PACMAN'sparticle sensor responded clearly to cooking sources and particles coming in from outdoors (probably woodsmoke) on winter evenings.

Results have been presented at the Healthy Buildings Conference in Brisbane (July 2012) and the International Society of Exposure Science Conference in Seattle (October 2012).

Further work is ongoing to ensure that we can use and interpret the data properly, allowing them to reliably identify the sources of indoor pollutants.

Recent PACMAN users include:

  • UNITEC, Auckland
  • University of Auckland, School of Architecture.
  • Wellington School of Medicine


Conference presentations:

  • Olivares, G., Longley, I., Coulson, G., 2012. Development of a low-cost device for observing indoor particle levels associated with source activities in the home. International Society of Exposure Science Conference, Seattle, October 2012.
  • Olivares, G., Longley, I., Coulson, G., 2012. Development of a low-cost device for observing indoor particle levels associated with source activities in the home. Healthy Buildings 2012, Brisbane, July 2012.
  • Longley, I.D., Gadd, J., 2011. Indoor PM10 measured in woodburning homes at 1 minute resolution. Conference of the Clean Air Society of Australia & New Zealand, Auckland, July 2011.
  • Longley, I.D., Gadd, J., 2011. High resolution PM10 in woodburning New Zealand homes. Indoor Air 2011, Austin, Texas, June 2011. 
Annotated photo of the PACMAN. Left: Sensors for CO2 (carbon dioxide), CO (carbon monoxide), PM (particulate matter, i.e. dust) and PIR (passive infrared, i.e. motion sensor), and a range finder (distance). Right: on/off power switch, AC power jack. Credit: NIWA
Placing one PACMAN indoors and one outdoors revealed dominance of outdoor sources on this cold winter evening and indoor sources the next morning. Credit: NIWA
PACMAN in situ in Auckland. Left top: 7 PACMAN units (white and transparent casings shown) measuring in a test home. Air quality sensors are on the top row and motion/distance sensors in the front. Bottom left: A suite of high quality research instruments for measuring particles and carbon monoxide/dioxide used for calibrating the PACMAN. Right: An ordinary Auckland home, used by the NIWA team for testing the PACMAN technology. Credit: Ian Longley