“The Air on the Bus Goes Round and Round; an Industrial Hygienist’s Look at Public Transit Vehicle Indoor Air Quality.”

Date / Time:

Wednesday - June 14th, 2023 / 12pm noon - 1pm PST


With headlines like “Second-hand fentanyl fumes threaten Seattle bus drivers,” transit ventilation has

become a mass media buzzword. A number of industrial hygiene and public health authorities are

currently studying this issue from engineering, toxicological and other perspectives. Today’s

presentation will focus on ventilation research by Sound Transit, Community Transit and the UW DEOHS

Field Research Group in cooperation with NASE, NIOSH and public health agencies. 


Ariel Piedmont, CIH, CSP is the Environmental, Health and Safety Manager for Community Transit, the

public transit authority of Snohomish County, Washington and was previously employed for 5 years as

Sound Transit’s Industrial Hygiene Program Manager. Ariel is also a panel member for the actively in

progress National Academy of Sciences Transit Cooperative Research Program addressing Air Quality in


Meeting topics will include:

  • General characteristics of public transit vehicle ventilation systems with respect to filtration and outside air exchange (various buses, light rail vehicles and commuter trains).
  • Available guidance (ASHRAE outside air recommendations for ground transportation, ASHRAE COVID-19 recommendations).
  • Adapting Jeff Burton’s methods described in Six Ways To Approximate Airflow; Simple Techniques for Assessing Airflow in Occupied Spaces June/July 2918 Synergist article to the transit environment https://synergist.aiha.org/201807-six-ways-to-approximate-airflow
  • Using human generated CO2, industrial CO2, propylene glycol aerosol and bee keeper’s smoke and associated CO to estimate outside airflow and in situ HVAC filtration efficacy challenge testing.
  • Process used to upgrade a bus fleet’s HVAC filter’s from MERV4 and MERV7 to MERV11 when the manufacturer initially said it couldn’t be done
  • Process currently being used to pilot test the feasibility of upgrading a bus fleet’s HVAC recirculated air filters from MERV7 to MERV13.
  • Work being done to optimize a solution that addresses all transit IAQ issues which can include indoor and outdoor generated pollutants.

Meeting Format:

Hybrid - Virtual and In-person options

Virtual on the Zoom Platform

In-person venue at UW DEOHS, 4225 Roosevelt Way NE, Suite 100, Room 2228 'The Fishbowl' Seattle, WA 98195

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Meeting ID: 943 7775 7413

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·        All are welcome to attend. If you plan to attend in person or virtual, please RSVP by June 12th to ensure there is capacity. Contact ce@uw.edu with questions.

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