Understanding PPM for Ozone Generators
If you read the first section of this mini-lesson, you will have a simple understanding of PPM for ozone generators. If not, click here to read "How Much Ozone is Enough?" This is a very important aspect of the ozone business, and critical to making choices for an ozone machine. The industry suffers from the hype-meisters who use YouTube or Google Adwords to grab the interest of ill-informed people to buy their equipment. Knowing how to make an informed decision will not come from "Researching the Internet", and that is because there is a lot of poor and misleading information on the Internet that will jaundice most people's decisions.
So, let's go back to the ASHRAE and EPA division point, "0.050 PPM is the maximum allowable ozone concentration recommended by ASHRAE in an air conditioned and ventilated space." And, "0.050 PPM is the maximum ozone concentration produced by electronic air cleaners and similar residential devices according to the proposed amendment of the Federal Food, Drug and Cosmetic Act." This is still a moving discussion, but OSHA says that safe levels of ozone should not exceed 0.10 PPM over an eight hour period. See OSHA Ozone Requirements
So, here's the short version of an otherwise complicated formulation. Residential or workplace ozone generation should not exceed these 0.050 to 0.10 PPM levels. Therefore, many units generate from about 500 mg/hr to 5000 mg/hr to stay under these safety levels. But, remember these apply only to using ozone generators when people are present. That is the BIG DIVIDE FOR OZONE GENERATORS. Air purifiers, therefore, are meant for use when people or pet are present. They are by the very nature of the requirements small scale machines with smaller ozone output.
But, small ozone units yearn to be big ozone generators. So, we see dozens of ozone-type air purifiers making claims for large scale odor removal, sanitizing, and mold kill. This is were stupidity exceeds honestly. A 500 mg/hr unit in a closet can do all this, but not in the whole house. The cannot reach the PPM necessary for serious impact. Referring the our St. Patrick's Day illustration of the previous article, the 5 gallon bucket will dye a 10 foot square area green, but not the whole river. The river is too big for the dye to fully impacted.
So, will these small ozone-type air purifiers deodorize, sanitize, and kill mold. Yes, and a thimble of water will refresh a man dying of thirst for about 30 seconds. True ozone generators have one constant rule. Commercial ozone generators are so powerful that people cannot stay in the room or building while they are operating. They can only be operated when people are vacated and those inside have proper personal protection equipment (carbon filter masks). So, we conclude that somewhere around 2000-5000 mg/hr units are the breaking point between air purifiers and ozone generators (depending on the size of the area treated).
Having too small an ozone generator is like asking a dog to pull a wagon that requires a horse to effective take a trip of more than 10 feet. It can be done, but how foolish! It is time that we stopped the games, hype, and over-sale of ozone-type air purifiers that pretend to be commercial grade machines. It is also time for ozone machine manufacturer to get honest. The National Ozone Association uses a standard 1000 cubic foot room to measure the true PPM for ozone machines. Some, well-known machines could not raise the level above 2 PPM, which means that they are inadequate for commercial use when you are usually dealing with much larger spaces.
A commercial application should raise the PPM level to at least 6 PPM for a period of 3-4 hours duration. If the manufacturer suggest a 24-48 hour application, he is compensating for the low volume. This will help, but likely not solve the really odor/sanitizing/mold problems that are in the building. To level the playing field, the easiest way to determine the strength of a unit is in a fixed area of 1000 cubic feet and a measurement of the PPM at 90 minutes of full operation. The National Ozone Association offers this service for any ozone generator willing to have an honest review of their equipment that the public can trust. However, when purchasing an ozone generator for commercial use, size does matter, training is critical, and safety rules. To find a list of NOAI approved ozone generators, see NOAI O3 Equipment
As the commercial ozone business grows, the need for better standards seem obvious. The National Ozone Association works to bring professionalism to this much needed service industry.