GroundTRUTH Lab Toronto Metropolitan University

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Low-cost indoor air monitoring for communities

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GroundTRUTH deploys custom, affordable systems for monitoring temperature, humidity, carbon dioxide and fine particulate matter in homes, including places without household Wi-Fi or building automation systems. Field deployments in Saskatchewan and Toronto are paired with testing against reference instruments so the measurements can be interpreted credibly and their limits remain visible.

Monitoring that works in more homes

The lab has deployed monitoring kits in more than 30 buildings, including homes in two on-reserve communities in Saskatchewan and homes in Toronto. Their low cost and independence from household Wi-Fi make longer-term monitoring possible across a wider range of housing.

Making low-cost measurements trustworthy

Affordable sensors can follow changes in indoor conditions without necessarily reporting the correct absolute concentration. GroundTRUTH compares them with reference instruments and tests multiple units of the same model to establish what each device can measure reliably and where calibration or cautious interpretation is needed.

From testing to real-world questions

The same monitoring infrastructure supports research on housing conditions in Saskatchewan and indoor exposure during Toronto wildfire-smoke events. In summer 2025, sensors in 15 Toronto dwellings were used to examine how outdoor smoke, building envelopes and indoor activities affected particulate matter concentrations inside homes.

How the sensors are tested

Four air-quality instruments co-located on a desk: two reference instruments and two consumer-grade monitors
Testing side by side. Lighthouse and Graywolf reference instruments were placed beside AirGradient and Airthings consumer monitors in an occupied home.Figure 2 from Zaky, Li and Stopps (2025), Journal of Building Physics. CC BY-NC 4.0.
Two time-series charts comparing carbon-dioxide readings from Graywolf, Airthings and AirGradient monitors at five-minute and thirty-minute intervals
Accuracy and precision are different. Airthings stayed closer to the reference CO2 concentration; AirGradient followed the shape of the changes more consistently but read low.Figure 3 from Zaky, Li and Stopps (2025), Journal of Building Physics. CC BY-NC 4.0.

Research collaborators

  • Tianyuan Li (University of Waterloo)
  • Sarah Haines (University of Toronto)

Students & trainees

  • Odel Linetska (PhD)
  • Rachel Tyli (PhD, University of Toronto)
  • Noor Zaky (MASc, completed 2025)
  • Vanitha Mathur (MBSc, completed 2025)
  • Carolina Espinoza Sanhueza (Postdoctoral Fellow, 2025–2026)

Papers