ASHRAE Journal - January 2021 - 84

Combating COVID-19 With Healthy
Ventilation Rates
By Glenn Esser, Application Engineer, Air Measurement at Ruskin®
As the novel coronavirus continues its global spread, ensuring healthy indoor air quality can play an important role in reducing
infections. Studies have demonstrated that increased fresh air ventilation has a direct impact on lowering the spread of microbial
contaminants in workplaces and other occupied spaces. ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality,
specifies minimum ventilation rates and other measures for new and existing buildings to provide acceptable indoor air quality
that minimizes adverse health effects.
Increasing Outdoor Air Intake
Demand control ventilation (DCV), which adjusts outside
ventilation air based on the number of occupants and the
ventilation demand those occupants create, is seen as a convenient
solution to satisfy ASHRAE 62.1. However, this type of control is
often left to the end-user, with few specific guidelines to calculate
the correct ventilation rate. This creates control levels that are
subject to interpretation and often inaccurate.
If building operators are currently using demand control
ventilation, ASHRAE 62.1 states that when the building is
occupied, no less than the amount of air necessary to meet the
building component must be introduced anytime the space is
occupied. An increase in outdoor air intake will help slow the
spread of bacteria and viruses. Facility managers should increase
the outside air setpoint to bring in more outside air.

Ruskin offers many solutions, including custom
combinations with products like the TDP05K.

Ensuring a Correct Outdoor Air Balance
The benefit of higher levels of outside air intake is that it helps slow the rate of microbial growth - including viruses such
as COVID-19. Unfortunately, outdoor air intake is one of the most difficult air measurement applications and is often done
incorrectly. System designs are typically 500 feet per minute for 100% outdoor air. However, end-users typically want to control
to the minimum rate, which is often set as low as 10% outdoor air. At that rate, the velocity of 50 feet per minute is much lower
than prevailing outside breezes and is very difficult to measure accurately when national average wind speeds are closer to
11 miles per hour.
When CO2 levels are being measured in the return air, as opposed to in an area near breathing level, it will show a lower CO2
indication than what occupants are breathing. Also, since outside air CO2 levels continue to rise, precise measurements of outdoor
CO2 levels along with indoor CO2 levels are critical to maintain differential PPM calculations. When only an indoor level is
used for a differential calculation based on assumed outside air CO2 levels that have gone up, the effect is less outside air is
being introduced to the space. Building owners and facility managers should review their operating sequence in the interest of
safeguarding occupant health and safety. For example, if the building's sequence has a max or target CO2 setpoint of 1,100 PPM
or more above background, consider reducing that target to introduce more outside air.
Providing a Cost-effective Solution
Facility managers should also check that outside air intakes, air measurement stations and outside air dampers are working
correctly, and that air filters and moisture eliminators are clean and free of obstructions.
While these efforts may increase the energy cost to condition spaces, it is currently among the most cost-effective and socially
responsible ways to keep schools, universities and places of business free from the spread of colds, flu and unwanted viruses,
including COVID-19.
For every airflow project and its unique design requirements, including efforts to help combat the spread of COVID-19,
Ruskin can help you find the right solution.

ruskin@ruskin.com | 816-761-7476 | ruskin.com

http://www.ruskin.com

ASHRAE Journal - January 2021

Table of Contents for the Digital Edition of ASHRAE Journal - January 2021