Before starting Forever Ozone I was an indoor air quality (IAQ) tester and sold air purifiers, mold test kits and in-duct UVC units, online and in a store in Henderson, NV. I got out of that business because I kept seeing the same thing: customers had air purifiers, yet a particle counter five feet from their tabletop unit read almost as if there was no purifier at all. Here’s what I learned and what I do in my own home.
The problem is airflow, not the filter
HEPA filters work. The small machines they’re in just don’t move enough air. Most tabletop units move a few hundred cubic feet per minute (CFM) or less. Your HVAC air handler moves thousands of CFM and is designed to change the air in your home about twice an hour. We kick up dust every time we move, so a small unit is only cleaning its own bubble.
What matters is CADR (clean air delivery rate): airflow times the percentage of particles removed. A HEPA filter catches a higher percentage than a MERV 11, but at a fraction of the airflow it still loses on total dust removed. If a purifier doesn’t publish a CADR, be cautious. Some well-built high-airflow units, like Airpura’s 360-degree design, do move enough air, but on high they’re loud.
If you have an HVAC system
- Run the fan in the “On” position. Most HVAC fans draw roughly 100 to 200 watts, so it’s a modest add to the electric bill.
- Use a MERV 11 filter and change it every three weeks or so. Most household dust is about 3 to 10 microns, which a MERV 11 captures well at HVAC airflow. They run about $5 each by the case. It’ll come out dark gray, which means it’s working.
- Consider an in-duct UVC lamp. Around $100. Easy if you’re handy, but I recommend a licensed electrician.
- Bring in fresh air as often as you can, avoid smoking indoors and use chemical-free cleaners.
- Vacuum without blowing dust around. I use a water-filtration vacuum that pulls dirt into water instead of a bag.
- House plants are a nice natural touch. Take them out of the room before a shock treatment.
No HVAC? The box fan and MERV 11 solution
When I moved into a beach condo without central air, I went back to my old bag of tricks. Nothing moves more air for the money than a 20″ metal-frame box fan (about $22 to $28; I like Lasko, made in the USA, over 2,000 CFM). Strap a MERV 11 furnace filter to it and it removes more dust by volume, much faster, than a typical mid-range purifier. This video shows the idea in action: box fan and filter test.
Tip: take the filter outside weekly and blow it out with compressed air, or vacuum the intake side while the fan runs. It’ll last months.
A small purifier still makes sense in one spot: your bedroom while you sleep, when you’re not stirring up dust.
What filters can’t do: surfaces, odors and VOCs
A filter only catches what floats through it. It doesn’t touch odors, chemical off-gassing from building materials and furniture, or what’s settled on surfaces, closets and ductwork. Dust mite droppings, a major indoor allergen (EPA overview of dust mites), settle and get kicked back up all day.
That’s where an ozone shock treatment of the empty home comes in. Run it while nobody is home (no people, pets or plants), with a timer that shuts off at least an hour before anyone returns, then open the windows and air it out. For VOC off-gassing, several treatments over days or weeks work best. I once sold ozone generators to a furniture contractor who ran ozone on and off for about a week before shipping pieces that had to pass a VOC test.
Sizing a whole-home shock treatment
Treat the whole structure at once; room by room lets untreated areas re-contaminate treated ones. The rule of thumb is about 1,000 mg/h per 100 square feet in dry air. At about 50% humidity, plan on roughly double, and for heavy smoke odor, double again. Example: a 2,000 sq ft home needs about 20,000 mg/h in dry air, about 40,000 mg/h at 50% humidity. See the Ozone Sizing Guide.
Our Commercial Grade machines use removable quartz tubes and solid state transformers with no exposed high-voltage wiring. Unlike ceramic plates, which can shed nano-metal particles as they wear (see the patent), our quartz tubes are nano-metal free. Details: Quartz Tube vs Ceramic Plate Ozone Generators. Step-by-step safety: Ozone Shock Treatment Advice.
The short version
- HVAC fan on, MERV 11, change every three weeks.
- No HVAC: box fan plus MERV 11.
- Optional in-duct UVC.
- Periodic ozone shock treatments of the unoccupied home, especially before moving in.
We answer the phone and give free advice after the sale. Call if you’d like help sizing your home.
Very interesting! Thank you for this article – one question: What happens when an Ozone Generator is run inside a closed container (such as the furniture trailer) to the point where all the available oxygen has been converted to ozone? I’m thinking about building a box for FedEx, UPS, and USPS to deposit deliveries. An interlock switch on the lid will turn on an ozone generator so that the packages will be sterile before I take them into the house. I am also considering a low volume ozone generator for inside the refrigerator, to put an end to moldy bread and cheese. Hence the question. Advice and purchase options would be appreciated.
Hi James.
The best approach would be using a 5g water ozonator and inserting the silicone tube via a small hole into the container. That way,
you have unlimited fresh air outside of the container to produce ozone. It comes inside of a 50 cal ammo box (strudy) and easy to
move around. It can also be fed via an oxygen tank or oxygen concentrator to make even high concentrations of ozone.