Ozone Safety

Ozone Safety

EPA / OSHA Information

The Food and Drug Administration (FDA) requires ozone output of indoor medical devices to be no more than 0.05 ppm (parts per million).

The National Institute of Occupational Safety and Health (NIOSH) recommends an upper limit of 0.10 ppm, not to be exceeded at any time.

EPA’s National Ambient Air Quality Standard for ozone is a maximum 8-hour average outdoor concentration of 0.08 ppm.

If an ozone air purifier is going to be running while people are present, the EPA recommends the proper settings should be selected so that the ozone level is less than 0.08 ppm.

PRO-4 Ozone Generators

For example, the PRO-4 operating for only 15 minutes every hour with the ozone output turned to it’s lowest position, will effectively treat a small room approximately 12′ by 12′ for extended periods of time, without exceeding the recommended ozone level.

For best results the ozone generator should be mounted as high in the room as practical. Ozone is heavier than air and it will eventually fall to the floor.

Air circulation is an important factor in how effective ozone works. For large areas, an oscillating fan should be placed next to the generator to help circulate the ozone throughout the room.

If the room is larger, these run times, or settings, can be increased accordingly. A simple test is to let your nose be your guide. Residual ozone becomes apparent to sensitive humans in the range of .01 – .03 ppm. or well below the permissible levels for continuous exposure.

If you can detect a strong smell of ozone, from 8 to 10 feet away, reduce the settings, or run it for less time. Detecting only a faint smell or none at all is a nice safe level.

There are numerous applications for ozone generators where people are not present and thus ozone levels are not necessarily of concern.

For example, the FM-2, or any of our other machines can be operated on their high settings continuously in an unoccupied basement to kill mold and mildew, or get rid of objectionable odors.

The FM-1, FM-14 or the PRO-8 should not be used in occupied spaces, unless that space is quite large, like a church or a barn.

For situations where heavy odors have built up in a room, we recommend setting the unit to high out put, shut the doors and windows, and let it run continuously for 3 or 4 hours while you and the pets are out of that room.

After the allotted time, turn it off, open the windows, and air out the room until the ozone has dissipated.

None of the ozone generators require expensive filters. A small fan filter is supplied with every unit and simply needs to be washed occasionally. The ozone plates located inside the generator should be cleaned with soap and water every 2 or 3 months, and replaced about every two years, or more often if there is a noticeable drop in ozone output. l.

History of Ozone use

Ozone application history


 Physical Properties of Oxygen and Ozone

Molecular FormulaO3O2
Molecular Weight48 g/mol32 g/mol
ColorLight blueColorless
SmellOdor threshold of 0.001 ppm, pungent at high levelsOdorless
Melting Point-192.5 deg C-218.79 deg C
Boiling point-111.9 deg C-1892.95 deg C
Critical Temperature-121 deg C-118.56 deg C
Critical Pressure54.5 atm5.043 atm
Density2.144 g/l @ 0 deg C1.429 g/l @ 0 deg C
Solubility @ 0 deg C0.64 g/100 ml0.049 g/100 ml
Electrochemical Potential2.07 V1.23 V

While ozone is the triatomic form of oxygen the differences in physical properties are vast.  While oxygen is not detectable by the human nose, ozone has an extremely low odor threshold.  Humans have the ability to detect ozone before many expensive measuring devices.  Also, ozone in air at high levels (greater than 0.1 ppm) is hazardous to human health.

The solubility of ozone is 13 times greater than oxygen.  While ozone still requires mechanical mixing devices to be dissolved into the water the ability to be dissolved into water is much greater than oxygen, and therefore lends ozone to be useful in many water treatment applications.

The electrochemical potential of ozone is much higher than oxygen which leads it to be one of the most powerful oxidants on earth.  This oxidation potential allows ozone to break down contaminates and kill bacteria faster than most every chemical alternative.

Chemical structure of ozone

Three molecules of oxygen will recombine to form two molecules of ozone. Two of an ozone molecule’s three atoms are bonded strongly, as in oxygen. The third atom is loosely bonded, making ozone gas 10 times more soluble in water than oxygen. Ozone has 24 protons, 24 neutrons, 24 electrons, and an atomic weight of 48. In
comparison to oxygen, where atoms are linked in a straight line, the ozone molecule is bent at a bond angle of 116.8°, a configuration that makes the ozone molecule more electrically active.

Consequences of Ozone Properties


  • Short half-life; Must generate ozone on site with ozone generating equipment. 
  • Ozone must be used shortly after it is produced.  Therefore, the ozone equipment must be sized for the peak ozone demand.  In systems where high levels of ozone are required for short periods of time the ozone equipment must be sized for that peak demands as no buffer, or storage of ozone is possible.

Partially Soluble Gas

  • Requires mechanical gas/liquid contacting.  While ozone is more soluble in a liquid than oxygen, it will still require contact basins, venturis, or other devices to mix ozone into water. 
  • Ozone has the tendency to off-gas back out of liquid causing safety concerns.  Ozone Solubility Info Here

Strong Oxidant

  • Material compatibility can cause problems – list of acceptable materials is short
  • Secondary reactions must be considered

Detection – difficult to monitor

  • Ozone breaks down upon contact with sensor cell.
  • Ozone has low vapor tension, does not fill room uniformly
  • Leaks can be difficult to find


  • Short-term health hazards with ambient ozone