How to Build an Ozone Sanitizing Chamber

The concept of an ozone sanitizing chamber is pretty simple, but there are some important basics to the process.  By following these critical elements, it is possible to scale from a small container to a large room depending on the cubic feet required for your needs.

Oxygen is a powerful and wonderful substance found in nature.  It is a replenishable resource as it is readily available and leaves no chemical residue.  Ozone is just another form of oxygen (O2) that is reformed into ozone (O3) by an ozone generator.  Oxygen readily cycles from O2 to O3, and then back to O2 without any difficulty.

Ozone does several things very well.  Ozone is fundamentally an oxidizing process.  This oxidation process has several levels of impact.  It can oxidize organic matter, hastens decay, rusts metal, and destroys pathogens. 

For decades ozone has been used to kill pathogens.  Ozone injections into large aquariums destroy the bacteria and viruses that would kill the fish.  Ozonated water is used to sanitize eggs, fish, and soda bottles before filling.  

The Primary Rule for Ozone Treatments

Ozone is what might be viewed as a richer form of oxygen.  The liability of using ozone is that high levels of ozone are a respiratory irritant.  Excess ozone will irritate the mucus membrane of the nose, throat, and lungs.  Exposure to higher levels of ozone will cause a tickle cough that passes once back into the fresh air.  An extended exposure to high ozone levels can cause a tired lung feeling as though you had run a race. 

Therefore, there is a universal rule for using ozone in any building.  Vacate the area of people and pets.  Secondly, be sure that there are no vents, pipes, or leaks into other areas of the building.  Exfiltration of ozone means that the ozone may leak into unintended areas.

The Sanitizing Chamber

With that simply stated, we can then turn to the basic parts of an ozone sanitizing chamber.  There are a few parts to building an ozone chamber.

  1. The ozone generator.  Depending on the cubic feet of the chamber/room, the ozone generator needs to feed into or be place inside the chamber.
  2. The chamber is a big variable.  It can be a 4’ by 4” box or a 20’ by 20’ room.  The challenge is that the math to formulate a chamber is rather loose.  
  3. The exhaust fan needs to be a small pipe vent with a fan that will draw the air out of the chamber into the outside air.  This creates a negative air pressure that greatly reduces the risk of exfiltration though crack, leaks, or conduits.
  4. An ozone meter allows the user to determine the ozone level available in the room.  This is preferred as math calculations rarely work out as expected.  

There are varying opinions on the level of ozone, which is calculated in ppm (parts per million).  For sanitizing, the low side is about 3.5 ppm, and the high side is 5-6 ppm.  Basically, these are modest levels as professional ozone shock treatments may exceed 12 ppm.  

Your problem is not too much ozone, but the time of application.  The treatment cycle is suggested to be 30-60 minutes.  These numbers seem to be the broad consensus on sanitizing.  

The ozone meter will report the ppm levels to assure an effective treatment.  

Controlling the exhaust fan will allow the operator to reduce or raise the ppm of the ozone.

Getting it Right

The makeshift nature of ozone sanitizing has many variables.  The size of the chamber, the items that are placed in the chamber, the humidity in the air, and the temperature.  

The size of the ozone generator will be one of the obvious questions.  Knowing that anyone using an ozone chamber will have to test, adjust, and measure the actual process; it has been commonly thought that it takes about 10,000 mg/hr of ozone generation for every 1000 sq ft.

Small chambers, therefore, could get away with 5,000 to 10,000 mg/hr.  Larger rooms might look for 10,000 to 30,000 mg/hr.  

Note that if the ozone generator is producing higher than 6 ppm, you can shorten the time or vent more air out of the chamber.  Just keep the process between the recommended 30 to 60 minutes.  

Take note to seal the ozone chamber to avoid leaks; but if air is being drawn from the room, you will need to plan for a fresh air inlet.  Exhausting the air creates a negative pressure out of the room, which is a safety concern so the ozone does not spread into unintended areas.

You will find a pipe in the hardware store that has a flap (like a dry exhaust flap) that allows air to flow into, but not back out, of the room.  The same furnace parts section will likely have a 3” to 6” pipe with a built-in fan that makes the process simpler.  A 3" round air cust pipe with a mounted fan is available at most hardware stores.  Use this fan to pull air out of the room as an exhaust into the outside air.

The exhaust air should match the inlet air, this creates a negative air flow that mitigates the seepage of ozone elsewhere.  There is no need for large air movement, but the goal is to create the negative air pressure in the room.

Air circulation inside the room allows the ozone to evenly treat all sides of the material inside the chamber.  Do not pile items on top of each other which may reduce ozone exposure.  Building wire shelves and hangers should keep in mind that all surfaces need to be exposed to the air.

A circulating fan is recommended when the chamber is a room.  This comes down to a practical approach to allowing the ozone to treat the items in the room.  You will not need a high velocity fan, but perhaps a low speed rotating fan that gradually moves the air around the room.

Final Thoughts

As stated, there is not a lot of great science to build the ideal ozone chamber from scratch.  Our goal is to provide the basics for building an ozone chamber.  Anyone taking upon themselves this task will learn by doing.

Assurance of performance can come from test runs of the system and further testing of the treated materials.  You may even want to test the treated items by a lab if you are so inclined.  As sanitizing of microbial life is invisible to the eye, the only other way to affirm the effectiveness of the protocols used for your application is to do lab tests. Generally, the best recommendation is 5-6 ppm for thirty to sixty minutes to sanitize all types of pathogens.

The ozone smell is not a concern.  Bleach has a residual smell too.  The ozone smell will go away in a while, but the fresh smell confirms that the item has been treated.

Also, used face masks may have an odor and sweat issue prior to treatment.  Along with the sanitizing process, odors will be eliminated.  

The goal of this report is to give guidance to those taking on this task by preparing a less-than-lab quality ozone chamber.  Ozone is a well-known sanitizer that has been used for decades.  There no question that ozone is good science, a powerful oxidizer, and has been proven in hundreds of ways for commercial and industrial purposes.

Under the present emergency for surgical face masks and protective gear, an ozone generator can extend the supply of needed goods for the front line workers.

Repeated treatment of zone will have a long-term effect on elastic bands and plastic items may cause them to become brittle or lose their elasticity.  Eventually, some items may need to be discarded; but this process can allow for items to be used multiple times before they are thrown out.  Depending on the items being sanitized, it is likely that goods may be treated 12-20 times without damage to the elasticity.  

Admittedly, this article is a "Makeshift Idea" for a time when we need good and reliable ideas that gets key services past the present emergency.  Fortunately, the ozone saturation (ppm) levels are quite modest.  Depending on the size of the room, perhaps 20' by 20' an ozone generator with 20,000 mg/hr or more should achieve the sanitizing level.  Larger machines will easily drive the ppm over 12 ppm may shorten the time cycle from 60 to 30 minutes.  Again, unless you have an ozone ppm meter, it is impossible to provide precise directions.  Alternatively, lab test of your ozone chamber will confirm that your ozone chamber is doing the job.

Ozone Sanitizing References: