Definitions
These are a list of words that you might come across about ventilation and the spread of the COVID-19 virus.
Velocity of Air: How fast the air is moving in the space
Airflow/Circulation: The process of air moving through the space and ventilation system
HVAC Systems: Heating, Ventilation, and Cooling Systems. They control the temperature and humidity of air in an indoor space and pump air through the space using vents, while also pulling in air from outside to refresh the indoor air
Unit Heaters: a type of HVAC system that does not filter the air
Return Valve: valve in the HVAC that prevents reversal of the flow of air. It keeps the air moving in the intended direction though the system.
Refresh/Exchange Rate: how often new outdoor air is brought indoors by the HVAC system
Fresh Air: new air from outdoors pulled into the HVAC system and then temperature controlled to pump into the space
Recycled Air: At normal recirculation setting, it is likely 50-80% of the air in the space is recirculated and the rest is fresh
Zone: an indoor space with recirculating air. An example of a zone is a breakroom, or a room in a warehouse
MERV: Minimum Efficiency Reporting Value is a measure of how effective a filter is at removing a specific size of particle. MERV 8+ have some ability to trap COVID-19 virus particles, but MERV 13+ is recommended
HEPA Filter: HEPA or High Efficiency Particle Absorbing Filters are very effective at removing COVID-19 virus particles from the air. HEPA filters remove 99.97% of all particles. 0.3 microns is the size that penetrates the MOST, and filtration is still 99.97%, so for all other sizes, larger and smaller (like COVID virus particles) the filtration is even higher.
