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Practical considerations for using low-cost sensors to assess wildfire smoke exposure in school and childcare settings



More frequent and intense wildfires will increase concentrations of smoke in schools and childcare settings. Low-cost sensors can assess fine particulate matter (PM2.5) concentrations with high spatial and temporal resolution.


We sought to optimize the use of sensors for decision-making in schools and childcare settings during wildfire smoke to reduce children’s exposure to PM2.5.


We measured PM2.5 concentrations indoors and outdoors at four schools in Washington State during wildfire smoke in 2020–2021 using low-cost sensors and gravimetric samplers. We randomly sampled 5-min segments of low-cost sensor data to create simulations of brief portable handheld measurements.


During wildfire smoke episodes (lasting 4–19 days), median hourly PM2.5 concentrations at different locations inside a single facility varied by up to 49.6 µg/m3 (maximum difference) during school hours. Median hourly indoor/outdoor ratios across schools ranged from 0.22 to 0.91. Within-school differences in concentrations indicated that it is important to collect measurements throughout a facility. Simulation results suggested that making handheld measurements more often and over multiple days better approximates indoor/outdoor ratios for wildfire smoke. During a period of unstable air quality, PM2.5 over the next hour indoors was more highly correlated with the last 10-min of data (mean R2 = 0.94) compared with the last 3-h (mean R2 = 0.60), indicating that higher temporal resolution data is most informative for decisions about near-term activities indoors.

Impact statement

As wildfires continue to increase in frequency and severity, staff at schools and childcare facilities are increasingly faced with decisions around youth activities, building use, and air filtration needs during wildfire smoke episodes. Staff are increasingly using low-cost sensors for localized outdoor and indoor PM2.5 measurements, but guidance in using and interpreting low-cost sensor data is lacking. This paper provides relevant information applicable for guidance in using low-cost sensors for wildfire smoke response.

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The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.


  1. Westerling ALR. Increasing western US forest wildfire activity: sensitivity to changes in the timing of spring. Philos Trans R Soc B Biol Sci. 2016;371.

  2. Spracklen DV, Mickley LJ, Logan JA, Hudman RC, Yevich R, Flannigan MD, et al. Impacts of climate change from 2000 to 2050 on wildfire activity and carbonaceous aerosol concentrations in the western United States. J Geophys Res. 2009;114:1–17.

    Article  Google Scholar 

  3. Naeher LP, Brauer M, Lipsett M, Zelikoff JD, Simpson CD, Koenig JQ, et al. Woodsmoke health effects: a review. Inhal Toxicol. 2007;19:67–106.

    Article  CAS  PubMed  Google Scholar 

  4. Urbanski SP, Hao WM, Baker S. Chapter 4 chemical composition of wildland fire emissions. Dev Environ Sci. 2009;8:79–107.

    Article  CAS  Google Scholar 

  5. Sekimoto K, Koss AR, Gilman JB, Selimovic V, Coggon MM, Zarzana KJ, et al. High-and low-temperature pyrolysis profiles describe volatile organic compound emissions from western US wildfire fuels. Atmos Chem Phys. 2018;18:9263–81.

    Article  CAS  Google Scholar 

  6. Simpson IJ, Akagi SK, Barletta B, Blake NJ, Choi Y, Diskin GS, et al. Boreal forest fire emissions in fresh Canadian smoke plumes: C1-C10 volatile organic compounds (VOCs), CO2, CO, NO2, NO, HCN and CH3CN. Atmos Chem Phys. 2011;11:6445–63.

    Article  CAS  Google Scholar 

  7. Wentworth GR, Aklilu Y, Landis MS, Hsu Y-M. Impacts of a large boreal wildfire on ground level atmospheric concentrations of PAHs, VOCs and ozone. Atmos Environ. 2018;178:19–30.

    Article  CAS  Google Scholar 

  8. Reid CE, Brauer M, Johnston FH, Jerrett M, Balmes JR, Elliott CT. Critical review of health impacts of wildfire smoke. Environ Health Perspect. 2016;124:1334–43.

    Article  PubMed  PubMed Central  Google Scholar 

  9. Cascio WE. Wildland fire smoke and human health. Sci Total Environ. 2018;624:586–95.

    Article  CAS  PubMed  Google Scholar 

  10. Doubleday A, Schulte J, Sheppard L, Kadlec M, Dhammapala R, Fox J, et al. Mortality associated with wildfire smoke exposure in Washington state, 2006-2017: a case-crossover study. Environ Heal. 2020;19:1–10.

    Article  Google Scholar 

  11. Cleland SE, Wyatt LH, Wei L, Paul N, Serre ML, West JJ, et al. Short-term exposure to wildfire smoke and PM2.5 and cognitive performance in a brain-training game: a longitudinal study of U.S. adults. Environ Health Perspect. 2022;130:1–12.

    Article  Google Scholar 

  12. Brumberg HL, Karr CJ. Ambient air pollution: Health hazards to children. Pediatrics. 2021;147.

  13. Holm SM, Miller MD, Balmes JR. Health effects of wildfire smoke in children and public health tools: a narrative review. J Expo Sci Environ Epidemiol. 2021;31:1–20.

    Article  PubMed  Google Scholar 

  14. Künzli N, Avol E, Wu J, Gauderman WJ, Rappaport E, Millstein J, et al. Health effects of the 2003 Southern California wildfires on children. Am J Respir Crit Care Med. 2006;174:1221–8.

    Article  PubMed  PubMed Central  Google Scholar 

  15. Aguilera R, Corringham T, Gershunov A, Leibel S, Benmarhnia T. Fine particles in wildfire smoke and pediatric respiratory health in California. Pediatrics. 2021;147.

  16. Chen C, Zhao B. Review of relationship between indoor and outdoor particles: I/O ratio, infiltration factor and penetration factor. Atmos Environ. 2011;45:275–88.

    Article  CAS  Google Scholar 

  17. Clark NA, Allen RW, Hystad P, Wallace L, Dell SD, Foty R, et al. Exploring variation and predictors of residential fine particulate matter infiltration. Int J Environ Res Public Health. 2010;7:3211–24.

    Article  PubMed  PubMed Central  Google Scholar 

  18. Sarnat SE, Coull BA, Ruiz PA, Koutrakis P, Suh HH. The influences of ambient particle composition and size on particle infiltration in Los Angeles, CA, Residences. Air Waste Manag Assoc. 2006;56:186–96.

    Article  CAS  Google Scholar 

  19. MacNeill M, Kearney J, Wallace L, Gibson M, Héroux ME, Kuchta J, et al. Quantifying the contribution of ambient and indoor-generated fine particles to indoor air in residential environments. Indoor Air. 2014;24:362–75.

    Article  CAS  PubMed  Google Scholar 

  20. Reisen F, Powell JC, Dennekamp M, Johnston FH, Wheeler AJ. Is remaining indoors an effective way of reducing exposure to fine particulate matter during biomass burning events? J Air Waste Manag Assoc. 2019;69:611–22.

    Article  CAS  PubMed  Google Scholar 

  21. Fazli T, Zeng Y, Stephens B. Fine and ultrafine particle removal efficiency of new residential HVAC filters. Indoor Air. 2019;29:656–69.

    Article  CAS  PubMed  Google Scholar 

  22. Azimi P, Stephens B. A framework for estimating the US mortality burden of fine particulate matter exposure attributable to indoor and outdoor microenvironments. J Expo Sci Environ Epidemiol. 2020;30:271–84.

    Article  CAS  PubMed  Google Scholar 

  23. Madureira J, Paciência I, De Oliveira, Fernandes E. Levels and indoor-outdoor relationships of size-specific particulate matter in naturally ventilated Portuguese schools. J Toxicol Environ Health. 2012;75:1423–36.

    Article  CAS  Google Scholar 

  24. Deng G, Li Z, Wang Z, Gao J, Xu Z, Li J, et al. Indoor/outdoor relationship of PM2.5 concentration in typical buildings with and without air cleaning in Beijing. Indoor Built Environ. 2017;26:60–68.

    Article  CAS  Google Scholar 

  25. Fang W, Song W, Liu L, Chen G, Ma L, Liang Y, et al. Characteristics of indoor and outdoor fine particles in heating period at urban, suburban, and rural sites in Harbin, China. Environ Sci Pollut Res. 2019.

  26. Buonanno G, Fuoco FC, Morawska L, Stabile L. Airborne particle concentrations at schools measured at different spatial scales. Atmos Environ. 2013;67:38–45.

    Article  CAS  Google Scholar 

  27. Parker JL, Larson RR, Eskelson E, Wood EM, Veranth JM. Particle size distribution and composition in a mechanically ventilated school building during air pollution episodes. Indoor Air. 2008;18:386–93.

    Article  CAS  PubMed  Google Scholar 

  28. Kirk WM, Fuchs M, Huangfu Y, Lima N, O’Keeffe P, Lin B, et al. Indoor air quality and wildfire smoke impacts in the Pacific Northwest. Sci Technol Built Environ. 2018;24:149–59.

    Article  Google Scholar 

  29. Allen RW, Adar SD, Avol E, Cohen M, Curl CL, Larson T, et al. Modeling the residential infiltration of outdoor PM2.5 in the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air). Environ Health Perspect. 2012;120:824–30.

    Article  PubMed  PubMed Central  Google Scholar 

  30. Boston Public Schools. INDOOR AIR QUALITY (IAQ) SENSOR DASHBOARD. 2023.

  31. Washington Air Quality Guide for School & Child Care Activities. WA DOH. 2022;DOH 334-33.

  32. Summary Wildfire Smoke Guidance for Closing Schools. WA DOH. 2022;DOH 334-43.

  33. US EPA. What is a MERV rating? 2023. Accessed 6/18/23.

  34. Coefield S. Mitigation measures in Missoula county. PowerPoint Present to EPA Smoke Manag Conf 2019;29–30, Seattle, WA. 2019.

  35. Pantelic J, Dawe M, Licina D. Use of IoT sensing and occupant surveys for determining the resilience of buildings to forest fire generated PM2.5. PLoS ONE. 2019;14:1–23.

    Article  CAS  Google Scholar 

  36. Sajani SZ, Trentini A, Rovelli S, Ricciardelli I, Marchesi S, Maccone C, et al. Is particulate air pollution at the front door a good proxy of residential exposure? Environ Pollut. 2016;213:347–58.

    Article  CAS  Google Scholar 

  37. Sahu V, Gurjar BR. Spatio-temporal variations of indoor air quality in a university library. Int J Environ Health Res. 2019.

  38. Strand T, Larkin N, Rorig M, Krull C, Moore M. PM2.5 measurements in wildfire smoke plumes from fire seasons 2005–2008 in the Northwestern United States. J Aerosol Sci. 2011;42:143–55.

    Article  CAS  Google Scholar 

  39. Delp WW, Singer BC. Wildfire smoke adjustment factors for low-cost and professional PM2.5 monitors with optical sensors. Sensors. 2020;20:3683.

    Article  PubMed  PubMed Central  Google Scholar 

  40. El Orch Z, Stephens B, Waring MS. Predictions and determinants of size-resolved particle infiltration factors in single-family homes in the U.S. Build Environ. 2014;74:106–18.

    Article  Google Scholar 

  41. Demokritou P, Kavouras IG, Ferguson ST, Koutrakis P. Development and laboratory performance evaluation of a personal multipollutant sampler for simultaneous measurements of particulate and gaseous pollutants. Aerosol Sci Technol. 2001;35:741–52.

    Article  CAS  Google Scholar 

  42. US EPA. AirNow Fire and Smoke Map Questions and Answers. 2022.

  43. Barn P, Larson T, Noullett M, Kennedy S, Copes R, Brauer M. Infiltration of forest fire and residential wood smoke: an evaluation of air cleaner effectiveness. J Expo Sci Environ Epidemiol. 2008;18:503–11.

    Article  CAS  PubMed  Google Scholar 

  44. Allen R, Larson T, Sheppard L, Wallace L, Liu S. Use of real-time light scattering data to estimate the contribution of infiltrated and indoor-generated particles to indoor air. Environ Sci Technol. 2003;37:3484–92.

    Article  CAS  PubMed  Google Scholar 

  45. Reche C, Viana M, Rivas I, Bouso L, Àlvarez-Pedrerol M, Alastuey A, et al. Outdoor and indoor UFP in primary schools across Barcelona. Sci Total Environ. 2014;493:943–53.

    Article  CAS  PubMed  Google Scholar 

  46. Shrestha PM, Humphrey JL, Carlton EJ, Adgate JL, Barton KE, Root ED, et al. Impact of outdoor air pollution on indoor air quality in low-income homes during wildfire seasons. Int J Environ Res Public Health. 2019;16.

  47. WA Smoke Blog 2020a.

  48. WA Smoke Blog 2020b.

  49. Shen H, Hou W, Zhu Y, Zheng S, Ainiwaer S, Shen G, et al. Temporal and spatial variation of PM2.5 in indoor air monitored by low-cost sensors. Sci Total Environ. 2021;770:145304.

    Article  CAS  PubMed  Google Scholar 

  50. Guo H, Morawska L, He C, Zhang YL, Ayoko G, Cao M. Characterization of particle number concentrations and PM2.5 in a school: Influence of outdoor air pollution on indoor air. Environ Sci Pollut Res. 2010;17:1268–78.

    Article  CAS  Google Scholar 

  51. McNeill VF, Corsi R, Huffman JA, King C, Klein R, Lamore M, et al. Room-level ventilation in schools and universities. Atmos Environ X. 2022;13:100152

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  52. BlueSky Canada Smoke Forecast. 2023. Accessed 6/6/23.

  53. Washington State Department of Ecology. Overview of smoke forecast map. Accessed 6/6/23.

  54. Fusina L, Zhong S, Koracin J, Brown T, Esperanza A, Tarney L, et al. Validation of BlueSky Smoke Prediction System using surface and satellite observations during major wildland fire events in Northern California. USDA For Serv Proc. 2007:403-8.

  55. Wang Z, Delp WW, Singer BC. Performance of low-cost indoor air quality monitors for PM2.5 and PM10 from residential sources. Build Environ. 2020;171:106654

    Article  Google Scholar 

  56. Morawska L, Thai PK, Liu X, Asumadu-Sakyi A, Ayoko G, Bartonova A, et al. Applications of low-cost sensing technologies for air quality monitoring and exposure assessment: How far have they gone? Environ Int. 2018;116:286–99.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  57. Demanega I, Mujan I, Singer BC, Anđelković AS, Babich F, Licina D. Performance assessment of low-cost environmental monitors and single sensors under variable indoor air quality and thermal conditions. Build Environ. 2021;187.

  58. Holder AL, Mebust AK, Maghran LA, McGown MR, Stewart KE, Vallano DM, et al. Field evaluation of low‐cost particulate matter sensors for measuring wildfire smoke. Sens. 2020;20:1–17.

    Article  Google Scholar 

  59. Holm SM, Balmes J, Gillette D, Hartin K, Seto E, Lindeman D, et al. Cooking behaviors are related to household particulate matter exposure in children with asthma in the urban East Bay Area of Northern California. PLoS ONE. 2018;13:1–15.

    Article  CAS  Google Scholar 

  60. Rai AC, Kumar P, Pilla F, Skouloudis AN, Sabatino SD, Ratti C, et al. End-user perspective of low-cost sensors for outdoor air pollution monitoring. Sci Total Environ. 2017;607-608:691–705.

    Article  CAS  PubMed  Google Scholar 

  61. Zusman M, Schumacher CS, Gassett AJ, Spalt EW, Austin E, Larson TV, et al. Calibration of low-cost particulate matter sensors: Model development for a multi-city epidemiological study. Environ Int. 2020;134:105329.

    Article  PubMed  Google Scholar 

  62. Jaffe DA, Miller C, Thompson K, Finley B, Nelson M, Ouimette J, et al. An evaluation of the U.S. EPA’s correction equation for PurpleAir sensor data in smoke, dust, and wintertime urban pollution events. Atmos Meas Tech. 2023;16:1311–22.

    Article  Google Scholar 

  63. Stampfer O, Farquhar S, Seto E, Karr CJ. School and childcare facility air quality decision-makers’ perspectives on using low-cost sensors for wildfire smoke response. BMC Public Health. 2023;23.

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We are grateful to the school and air quality agency personnel who hosted air quality sensors and monitors and partnered with us on this research. We thank Dr. Elena Austin, Amanda Gassett, Dr. Tim Gould, Dr. Tim Larson, Maria Tchong-French, and Jeff Shirai of University of Washington (UW) for their guidance and support in this research. We also appreciate support from Taylor Hendricksen, Kylie Milano, and Cristina Urrutia of UW. We are grateful for assistance with air sampling from Amanda Virbitsky, Megumi Matsushita (UW), and Annie Doubleday (UW).


This work was supported by the US National Institute of Environmental Health Sciences of the National Institutes of Health under Award Number #F31ES032634 and the University of Washington EDGE Center of the National Institutes of Health under award number P30ES007033. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. This publication was supported by the American Academy of Pediatrics (AAP) and funded (in part) by the cooperative agreement award number 5 NU61TS000296-02-00 from the Agency for Toxic Substances and Disease Registry (ATSDR). The U.S. Environmental Protection Agency (EPA) supports the PEHSU by providing partial funding to ATSDR under Inter-Agency Agreement number DW-75-95877701. Neither EPA nor ATSDR endorse the purchase of any commercial products or services mentioned in PEHSU publications. This work was also supported by the University of Washington Department of Environmental & Occupational Health Sciences Castner Award. The funding sources had no involvement in the conduct of research or preparation of this article.

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CRediT author statement Orly Stampfer: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project Administration, Software, Visualization, Writing - original draft, Writing - review & editing. Christopher Zuidema: Formal analysis, Methodology, Software, Writing - original draft, Writing - review & editing. Ryan W. Allen: Conceptualization, Methodology, Writing - original draft, Writing - review & editing, Supervision. Julie Fox: Conceptualization, Writing - review & editing Paul Sampson: Formal analysis, Methodology, Software, Writing - review & editing Edmund Seto: Conceptualization, Methodology, Funding acquisition, Writing - original draft, Writing - review & editing, Resources, Supervision. Catherine J. Karr: Conceptualization, Methodology, Funding acquisition, Writing - original draft, Writing - review & editing, Resources, Supervision.

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Correspondence to Orly Stampfer.

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Stampfer, O., Zuidema, C., Allen, R.W. et al. Practical considerations for using low-cost sensors to assess wildfire smoke exposure in school and childcare settings. J Expo Sci Environ Epidemiol (2024).

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