By Norm Grusnick, PEng, Commercial Business Development Representative, ECCO Supply
Over the past several years, a record number of wildfires in the Westen United States and Canada has sparked a renewed discussion about indoor air quality (IAQ). Building codes and ASHRAE’s Ventilation and IAQ Standards (62.1, 62.2) bases for achieving IAQ is through dilution and air cleaning, as well as ensuring air that enters or leaves a building in a controlled manner. In some instances, outdoor contaminants may be higher than indoors, universally measured by the air quality index.
IAQ During Wildfire Smoke
Wildfire smoke is a complex mixture of particulate matter and gases, including carbon monoxide, volatile organic compounds, and ground level ozone. Outdoor air pollutants, including smoke, enter and leave buildings in three main ways: mechanical ventilation, natural ventilation, and infiltration. Many of today’s tightly closed buildings reduce exposure to outdoor air pollution. Upgrading the filter efficiency of the HVAC system and changing filters frequently during periods of smoke greatly improves indoor air quality. See below for steps to take before and during a wildfire smoke event.
- Have your HVAC technician evaluate weather higher MERV filters can be used.
- Select a filter with the deepest pleat your system can accommodate—two inches or more.
- Understand that MERV rated filters remove particulates but not ‘smoke smell’ or most gases.
- Make sure filters fit tightly in frames to prevent bypassing.
- Have spare sets of filters on hand because they may not be available due to increased demand.
Filtering and Ventilation
Make sure ventilation is compliant with building codes. Directly measure or validate air flows by an accredited TABB professional. Note a TABB measurement is only good for a moment in time; systems are impacted by the environment and degrade over time. Inspect, maintain, and monitor all systems often. Ensure windows and doors are properly closed. Control the pressurization flow by ensuring the ventilation rates exceed exhaust and relief rates during all operation and dynamic reset modes. Disable demand control ventilation and economizer operation to limit dynamic modes of operation during wildfires.
Filtering, ventilation, and pressure control are the foundation of maintaining a healthy building during normal operation and essential during an outdoor event such as a wildfire. Integrating airflow measuring devices into a building automation system allows ventilation rates to be automatically adjusted as conditions change.
Buildings other than homes should have a Wildfire Readiness Plan. If your building has a building automation system, consider adding a Smoke Event mode to manage outside air intakes. Consult ASHRAE Planning Framework for Protecting Commercial Building Occupants from Smoke During Wildfire Events for more information.
Measure to Control
If you do not measure it then you can not control it. When designing or upgrading a mechanical system or setting up an HVAC system it is essential to prioritize measurement, control, and fault alerts as the foundation for these systems, New HVAC system designs should consider adding filtration efficiency and control strategies to initiate smoke mode. This will allow the systems to operate energy efficiently during normal mode and allow for additional fan capacity and control logic needed during wildfire events. Airflow measurement and control costs in an HVAC system are minimal compared to the future impact and cost due to over ventilation, inadequate ventilation, and infiltration. ■
