The benefit of higher levels of outside air (OA) intake brought in through HVAC systems is that more outside air will help slow the rate of microbial growth (including viruses such as COVID-19) by diluting the concentration of any contaminates that might be present in the air … such as smoke or any VOC (volatile organic compounds) odor.

As the winter months arrive, people will spend more time indoors. It will be important for HVAC contractors to ensure that outside air intake, along with ventilation rates for each space, are set to nothing less than the required minimum ventilation rates.

ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, specifies minimum outside air intake rates. More ventilation air changes per hour in a space, along with increased outside air intake when combined with other measures — most important of which is wearing a face mask at all times, washing hands frequently and maintaining social distance of six feet or greater will help to minimize adverse health effects.

Reducing the amount of virus-containing particles in a space is best accomplished by wearing a face mask. Ventilation and the introduction of outside air helps dilute and displace any air pollution in the space.

HVAC contractors should review the building’s air movement from supply vents to return vents and turn off ceiling fans that simply move the air around. The air handler’s operating sequence should be reviewed in the interest of safeguarding occupant health and safety.

Demand control ventilation (DCV), which reduces outside ventilation air based on CO2 parts per million (PPM) measurements should be overridden for conference rooms or set to “occupied” to bring in more ventilation air at all times, not just when levels reach some maximum temperature setpoint level.

Lower target CO2 PPM operating setpoints will bring in more air. For example, if the building’s sequence has a max or target CO2 setpoint of 1000 PPM, this is roughly 15 CFM per person. By lowering the target CO2 setpoint to 800 PPM, reducing the CO2 PPM target will introduce about 30 CFM per person.

When set to 100 percent outside air, the setpoint will be 400 PPM. More outside air can be more expensive to heat or cool depending on the temperature differential between indoors and outside. As a result, more outside air can increase utility costs.

HVAC contractors must take into consideration the trade-off between increased outside air ventilation (and subsequent higher utility costs) and the health of building occupants.

Will increasing the level of outside air ensure building occupants will not get sick? No, it will not. Is introducing more than the required minimum outside air better? Yes. However, bring in no more than the maximum outside air possible, remaining within the ability of the heating and cooling system to maintain comfortable temperatures and healthy indoor humidity levels between 40 to 60 percent.

HVAC contractors should check outside air intakes, air measurement stations and outside air dampers to confirm all are working correctly. Consider upgrading air filters from MERV 8 to MERV 13 or MERV 14, increasing the filtering of recirculated air.

Moisture eliminators on outside air intakes should also be clean and free of obstructions. It may be helpful to bring in a test, adjusting and balancing (TAB) contractor to confirm outside airflow is at the very least meeting minimum airflows as required by building codes.

Ruskin — a manufacturer of fire, smoke and control dampers, louvers and diffusers — has full line of air measuring products for HVAC systems that can be used to directly measure and control outside air intake.

We help HVAC contractors select the right air measuring products so your buildings will remain healthy, safe and energy-efficient.