Frequently Asked Questions

1What is the difference between an air filter and an air treatment?
Air filters remove particles from the air streamed through them.Air treatments—such as ultra-violet germicidal irradiation (UVGI) and ionization—treat the air passing by the treatment point.All Clean Air Curtains provide the highest possible level of filtration.Certain Clean Air Curtain models also offer the most effective UVGI treatment of particles that have already been captured by the HEPA filter.
2What is a HEPA filter?
HEPA stands for High Efficiency Particulate Air.The term “efficiency” refers to the percentage of particulates captured by an air filter.The hardest particles to capture are 0.3 microns in size.The Clean Air Curtain's HEPA filters capture at least 99.995% of ALL particles in the air that passes through them.
3How does a HEPA filter work?
HEPA filters capture the smallest particles using three different methods:DIFFUSION: Particle size LESS THAN 0.3 micron: these have so little mass (weight) they bounce around in what is called “Brownian Motion”, a random zig-zag pattern that causes the particles to hit the filter fibers and become trapped.INTERCEPTION: Particle size BETWEEN 0.3 and 1 micron: enter the filter openings and attempt to follow the air around the filter media. However, they are too heavy and some don’t move fast enough thus end up getting trapped in the filter media.DIRECT IMPACT & STRAINING: Particle size LARGER THAN 1 micron: too large to pass through the small openings in the filter media and become trapped on the filter surface.
4What does “efficiency” mean? How is it measured?
Efficiency refers to how effective an air filter is at capturing microscopic particles passing through it.Efficiency is measured by estimating the percentage of particles captured.
5What is a standard air filter?
Standard air filters are rated on a Minimum Efficiency Reporting Value, or MERV, with higher numbers capturing increasingly higher percentages of particulates and dust of increasingly smaller sizes.
6What does arrestance mean? How is it measured?
Arrestance refers to how effective an air filter is at capturing larger particles without becoming clogged.MERV 1 - 4 Less Than 20% Efficiency, 60 - 80% Arrestance, Larger than 10 microns MERV 5 - 8 20% - 60% Efficiency, 80-95% Arrestance, 3 - 10 microns MERV 9 - 12 40 - 85% Efficiency, 90-98% Arrestance, 1 - 3 microns MERV 13 - 16 70% - 98% Efficiency, 95-99% Arrestance, 0.3 - 1 micronsHEPA 99.995% Efficiency
7Why does efficiency matter?
Higher efficiency equals cleaner air.
8What size are the COVID-19 virus particles?
Individual COVID-19 particles are estimated to range from 0.06 microns to 0.14 microns. HOWEVER—airborne particles are often clustered together in larger groups
9What size are the particles in smoke from fires?
The EPA says wood smoke particles range in size from 0.4 - 0.7 microns.
10How good is the Clean Air Curtain’s HEPA filter?
The HEPA filter in the Clean Air Curtain is the best available: it captures 99.995% of ALL particles in the air that passes through it.In plain math, that means if there are 10,000 particles in a given volume of air passing through our HEPA filter—which would be about equivalent to an infectious person sneezing directly into the unit—only 5 of those particles would come out the other side.
11How good is the Clean Air Curtain’s UVGI Treatment?
The UVGI bulb the Clean Air Curtain models that include it is the best available: it inactivates--or kills--99% of virus particles within seconds, AFTER they are trapped and held by the HEPA filter.
12How good is the Clean Air Curtain’s exit velocity?
The exit velocity of the pure air coming from the Clean Air Curtain is the highest available on the market today in a portable, desktop device: 1,200 feet per minute.
13How good is the Clean Air Curtain’s effective distance?
The effective distance of the Clean Air Curtain is the highest available on the market today in a portable, desktop device: over 40 feet for the "1200" Series.
14What is Clean Air Exit Velocity?
Moving air is measured in feet per minute, or FPM. This is the actual speed—or velocity—of the air leaving the unit.
15Why does Clean Air Exit Velocity matter when choosing a filter?
The faster the air leaving the unit, the more effective it will be at mixing the cleaned air with the remaining air; AND The more effective it will be in separating individuals and protecting against person-to-person contagion.
16What is Clean Air Effective Distance?
The distance that the clean air from the unit improves and mixes the remaining air in the room.
17Why does Air Exit Direction matter when choosing a filter?
Air that flows sideways—past one person towards another—is a possible source of infection; the only safe direction for air to flow is up, as air that flows down will be directed sideways at some point.
18How often does the Clean Air Curtain’s filter need replacing?
The Clean Air Curtain uses three (3) filters: two (2) pre-filters and one (1) HEPA filter. These filters are estimated to last between three (3) and five (5) years before needing replacement.
19What is Clean Air Delivery Rate (CADR)?
CADR is the volume of filtered air delivered—at the exit—by an air filter, as measured in Cubic Feet per Minute, or CFM.
20Why do some devices say they deliver more than they actually do?
Some manufacturers use the fan or blower rating instead of measuring the actual flow at the exit of the unit.
21How Loud is 59 dB?
Most residences hover around 50 dB.A soft whisper from 5 feet away is around 40 dB.Office noise, or inside a 60 MPH car is about 70 dB.
22How much energy is 77W?
Typical lightbulbs range from 40W - 200W. Most large television sets use between 100W and 200W.
23Where should the Clean Air Curtain be placed?
We recommend a level surface somewhere between 3 and 6 feet in height, with at least 2 feet of space between the unit and any surface above it.Any location will be beneficial, but placing the Clean Air Curtain in a Dead Zone—defined as where air does not usually flow—will further help mix the air in the room.
24What are aerosols? Why do they matter?
An aerosol is a grouping of very small particles or liquid droplets suspended in air. Natural aerosols include fog, mist and dust. Human aerosols include car exhaust and exhaled breath. Aerosols can be visible, like fog; but are more often invisible in normal concentrations, like dust, pollen and viruses.
25How is COVID-19 spread?
It is widely understood that COVID-19 is spread by aerosols emitted by contagious people; these aerosols are either spread directly or linger in the air.
26What is the risk of “the air that we share”?
You are at risk whenever you share air with anyone—but especially others who are not in your bubble. The aerosols emitted by others may contain pathogens such as viral particles. This is how COVID-19 is spread, as well as the common cold and the flu.
27How do I determine my level of risk?
Key Risk Factors:The number of people vs. the amount of space The activities of the people The level of filtration & the amount of fresh airRisk increases with the number of others: 1 is better than 2, which is better than 3, etc.Risk increases with the number and volume of exhalations: just breathing is better than speaking, which is better than yelling, which is better than singing, which is better than shouting, etc.Risk increases with closeness: the smaller the space, and the closer people are to each other, the greater the risk.Risk DECREASES with better filtration an/or increasing amounts of fresh air.
28What is a well-mixed room?
A well-mixed room has few or no dead spots. In our work with clean rooms, we call them “dead zones”—where dust and small particles accumulate.In our modeling of rooms for pathogen risk—and how to reduce risk—we look for these dead zones as places where aerosols can concentrate.
29Do humans emit aerosols?
Yes. Absolutely. No doubt. A recent University of Minnesota study measured just how much. The Air Cleaners Inc CFD simulations used these measured values as the basis for our inputs.
30What is CFD?
Computational Fluid Dynamics uses computer processing technology to show how the air flows in a room, based on the real input details?
31What is UVGI?
Ultraviolet light germicidal irradiation—UVGI—is used to inactivate (kill) viral particles. The energy contained in the light damages the RNA of the viral particles—more energy for longer means more damage, just like sunburn.The effectiveness of UVGI is directly related to the wavelength of the light—UV-C is the best—and the intensity of the exposure—higher energy, longer and closer is better; again, just like sunburn or time in a tanning booth.
32How heavy is 32 pounds?
About the weight of a small microwave oven.
33What is ASHRAE?
The American Society of Heating, Refrigeration & Air Conditioning Engineers is an American professional association seeking to advance heating, ventilation, air conditioning and refrigeration systems design and construction. ASHRAE has more than 57,000 members in more than 132 countries worldwide.
34What is whole building UV?
Using UV to treat the air flowing through a building’s HVAC system. While this may effectively reduce a percentage of viral particles passing through the system—depending on the design of the system—it does nothing to address aerosols that are not brought through that system, dead zones or person-to-person contact.
35Is the UV-C bulb UL certified not to cause the emissions of ozone?
Yes, the bulb is UL certified and does not emit ozone. We have a complete unit at UL now undergoing system approval and expect certification at the "system" level by the end of this year (December expectation).
36Is the UVGI/UV-C light actually treating the air that flows through the device or treating the trapped particles on the HEPA filter?
Both. The UV light is positioned in the supply plenum, under the HEPA filter. It is designed to kill pathogens as they pass by it, and it's positioning is set to shine on the bottom of the filter. So any pathogens not killed in transit as they pass the light, will be killed within seconds by the UV light shining on them as they become lodged in the filter.
37How do you keep the HEPA filter from degrading so quickly in the presence of UV-C, as 3-4 years seems like a fairly long operational deployment for these parts w/o replacement (filter and bulb)...?
We do not yet have field data on how the process of filter degradation will occur. But the filter manufacturers are providing us with data that suggests the HEPA filters will last a long time. The filter is made from micro-fiberglass which, they are telling us, does not degrade appreciably due to UV exposure. Also, the UV light is not very large due to the small size of the package. So we are expecting the filter will last for 3-4 years. If it does degrade, we will replace it with another one—see our notes below regarding an extended warranty/service agreement. The bulb has a life expectancy of 11,000 hours of continuous life.
38National Academy of Sciences FAQ Link