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When we talk about sizing, we are referring to choosing the right model and quantity of Air Reactors for your indoor environment.  Basic sizing is pretty straight forward and is based on the air volume on each level of your home.  However, there are many other factors than can affect sizing and ultimately determine the proper deployment of Air Reactors for your home or business.

Basic Sizing

Each model of the Air Reactor was designed to address a set volume of indoor air under normal conditions. The table below gives the basic air volumes that can be effectively treated by each Air Reactor model.

Sizing Factors

HiTech Air Reactor Basic Sizing Table

(click table to enlarge)

There are several factors that can determine the required number of Air Reactors for your home or business.  We've highlighted a few of the most common ones below.  Keep scrolling to the bottom of the page for a example of how these are applied at an actual home.

​In general a minimum of one Air Reactor is required for each floor of your home, since most homes have inadequate air mixing between floors. 

HiTech Air Reactor Crawl Space Sizing

When calculating the air volume for homes with a crawl space, it is important to include the air volume of the crawl space in total air volume calculation for the first floor - unless you plan to locate an Air Reactor in the crawl space.

Active moisture or water intrusion situations will lower the total air volume that can be addressed by each Air Reactor.  A general rule of thumb is to reduce the air volume each Air Reactor can cover by half. This is important to ensure adequate Hydroxyl Radical concentration to overcome the mold and mycotoxins that are being produced.

HiTech Air Reactor Drop Ceiling Sizing

When calculating the air volume for indoor spaces with drop ceilings, it is important to include the air volume above the drop ceiling in total air volume calculation.

Most basements should be considered active moisture situations. The Model 110 is our most popular choice to address damp or musty basements.

HiTech Air Reactor Apartment Sizing

Apartments, condos and flats that share common walls with other units can experience contamination due to air exchanges from adjacent units. We recommend adjusting the maximum serviceable air volume to no more than 75% of nominal, to account for this cross-contamination. 

Sizing Example

Let's look at an example of how to apply the sizing basics and scaling factors to a typical home. The home below is a single story with 2,322 square feet of living area.  The ceiling height is 10 feet throughout the home, with the exception of a vaulted ceiling in the Living Room which has a peak of 18 feet in the center and 12 feet at the wall.  Since basic sizing of the Air Reactors is based on the total air volume in the home, we need to calculate the volume by multiplying the square footage by the ceiling height.

HiTech Air Reactor Floor Plan Sizing Example

Since there is a common ceiling height of 10 feet everywhere except the Living Room, we can determine the air volume of the home, excluding the living room, by subtracting the Living Room area from the total square footage of the home and multiplying by the 10 foot ceiling height:

So excluding the Living Room the home has 15,600 cubic feet of air volume.

Now let's calculate the Living Room air volume.  We can use the graphic to the right and the formula below to determine the Living Room volume:

The Living Room air volume is 11,430 cubic feet:

To obtain the total air volume in the home we now just add the two volumes we've calculated together:

So our total air volume for the home is 27,030 cubic feet.

Basic Sizing

Now using the basic sizing table at the top of the page we can see that each Model 101 Air Reactor can address up to 12,000 cubic feet of air volume per floor. To maintain adequate concentration of Hydroxyl Radicals we would need three (3) of the Model 101's to be properly sized for our example home (assuming there were no active moisture issues).

3 x

If we had an active moisture issue in the home then we would use a 1/2 scaling factor for the Model 101, which means each Model 101 covers 6,000 cubic feet of air volume and we would require five (5) of the Model 101's to be properly sized.

Sizing with Active Moisture Issues (Hostile Environment)


5 x

Additional Considerations

Crawl Space

Have you considered how the crawl space beneath your home contributes to the air quality in the living space? There is often little barrier between you and the crawlspace allowing odors, moisture, and mold spores to get drawn up into your living area.  This natural drawing of air up into the home is called the "Stack Effect."  It's the same principal found in a chimney.  Air is drafted from the low area where the fire is, and this air flow carries the smoke up and out through the top of the chimney.  Our homes act in a similar way, drawing air from the crawl space up through the interior of the home.

Many crawl spaces have dirt floors, high humidity levels, bugs and rodents and have a large number of penetrations in the sub-floor for wires, pipes, and HVAC duct work.  Each of these holes act as a mini chimney drawing contaminated air from the crawl space into the interior of the home.


If you have a traditional un-encapsulated crawl space beneath your home, it should be considered a hostile environment for sizing purposes.  This means when you calculate the air volume in the crawl space you should double this number when you add it to your first floor air volume.



In our example above, lets assume the entire 2,322 square feet have crawl space below them.  The crawl space has a distance between the ground and sub-floor of the first floor of 3 feet.  So the air volume of the crawl space is 6,966 cubic feet. Our air volume calculation for sizing purposes is 6,966 x 2 since we consider an un-encapsulated crawl spaces a hostile environment:


To calculate the total air volume for sizing purposes we add the first floor air volume of 27,030 cubic feet and the hostile crawl space scaled air volume of 13,932 cubic feet to get 40,962 cubic feet of air that must be addressed by the Air Reactors.

In this example to maintain adequate concentration of Hydroxyl Radicals we would need four (4) of the Model 101's to be properly sized for our home.

4 x

What if we redid this example with an encapsulated crawl space?  In that case we would use the calculated air volume of the crawl space and add it to the first floor air volume directly with no scaling as we wouldn't typically count an encapsulated crawl space as hostile.  Now our volume is calculated:

So we have a total air volume of 33,996 cubic feet and again with 12,000 cu feet per Model 101 we would need a total of three (3) Model 101's to be properly sized.

3 x

Negative Pressue

We discuss negative air pressure over on the Mold page and even show a video of how to test for it. If you find your home has a negative air pressure problem we would suggest sizing your Air Reactor deployment as if you were in a hostile environment. Negative pressure pulls all kinds of contaminates into your indoor air and as such places a larger load for the Air Reactors to overcome.

Contact us with questions!

We hope this page provided you with a basic understanding of Air Reactor sizing.  We realize not all cases are straightforward and you may need some assistance.  If you'd like us to review your home and situation in more detail and provide you with a recommendation, please head over to the Quote Request page and provide us with your details and we will put together a custom recommendation for you.

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