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SITE-SPECIFIC HEALTH AND SAFETY PLAN FOR PHASE II ENVIRONMENTAL SITE ASSESSMENT Potential Airborne Concerns and Air Monitoring Action Levels July 7, 2023 • The Level for Respirator Use is the concentration at which a respirator will be put on; it does not require the job to stop. The respirator is a tool to be used while determining why the exposure has reached that concentration. Take action to reduce the concentration using engineering controls such as water mist, spray foam, plastic cover, etc. • The Level for Work Stoppage is the concentration at which work on the job will stop. Determine why exposures have reached that concentration and how they can be reduced. Site evacuation is not necessary at this level. Implement engineering controls to reduce the concentration, and then resume work. • PIDs - Photoionization Detectors are used for general hydrocarbon monitoring; an example would be benzene, toluene, ethylbenzene, and xylene, common on gasoline station sites. The PID typically uses either a 10.6 eV lamp (responds to pentane and higher hydrocarbons), or 11.7 eV lamp (responds to ethane [weakly], propane and higher hydrocarbons)to ionize and detect the gas. The PID will measure hydrocarbons that are ionized, and therefore is a screening device, not a chemical-specific measurement instrument. Benzene Meter— RAE Systems UltraRAE 3000 PID/Benzene Monitor. • The Levels for Work Stoppage are based on measurements taken using PIDs calibrated with isobutylene; PIDs calibrated with gases other than isobutylene may have a different response factor. • Action levels can be modified with particular knowledge of contaminants and site conditions. • In the following cases, contact the HSSE MANAGER for guidance on the air monitoring requirements. o When calibrating with a calibration gas other than isobutylene. o When requesting to modify the values above. o On sites impacted with chemicals other than petroleum products. Stantec 4.5