Standard Temperature and Pressure: 273.3 K (O0 C, 320 F) and 1013.25 mb (14.706 psi)

Metric Volume and Length

1 m3 = 1,000 liters 1 gallon = 4.546 liters
1 foot = .305 meter 1 ft3 = .0283 m3
Ozone in Water
1 g/m3 = 1 mg/L = 1 ppm ozone (by weight) in water
Ozone in Air (Low concentrations such as work place safety)
(Concentrations by Volume)
1 g O3/m3 = 467 ppm by volume
1 ppm O3 (volume) = 2.14 mg O3/m3
1 ppm O3 (volume) = 214 ug/m3 (used more often in Europe)
1 ppm = .00214 ug/ml 1 ug/ml = 467 ppm (used in medical ozone)
1 ppm = 100 pphm (used in rubber testing)
Concentration by volume, v/v = C (g/m3) X 1733 X T/P = 467C at STP

Ozone in Air (High concentrations such as at the outputs of corona discharge generators)

(Concentrations by Weight)

1 g O3/m3 = 782 ppm by weight
100 g O3/m3 = 7.82% O3 in air
1% O3 (by weight) = 12.8 g/m3 in air
Conc. by weight, G (or w/w) = C X .29 X T/P = .0782C at STP, C = Conc. in G/M3
Ozone in Oxygen (High concentrations by Weight)

1 g O3/m3 (of O2) = 699 ppm by weight
100 g O3/m3 (of O2) = 6.99% O3 in O2
1% O3 (by weight) = 14.3 g/m3 in oxygen (OVER)

Output of Small Ozone Generators

Ozone output = (a constant) X (air flow through the generator) X (measured concentration)

For small generators this can be expressed as:

Output (g/hour) = K X (flow in cfm) X (measured ppm (vol))
= cfm X .0283 m3/ft3 X 60 min/hr X ppm (vol)/467 ppm/g/m3
(17) Output (g/hr) = .00364 X cfm X ppm = .128 X m3/min X ppm
Typical Instrumentation Ranges by Application
Ambiental ozone: 0-1 ppm (volume)
Ozone for storage, etc. 0-20 ppm (volume)
High concentration ozone: 0-16% by weight 0-200 g/m3 (note if O2 or air)
Ozone dissolved in water: 0-20 mg/L 0-20 ppm (by weight)
Important Qualitative Ozone Relationships

Ozone half-life in air is typically about 15 minutes in open areas (can be hours in enclosed areas) and increases with lower temperature and lower humidity.

Ozone is about 50% heavier than air and has a low vapor pressure, so it tends to sink to the floor and does not disperse if there is no air circulation.

Virtually all ozone instruments have cross-sensitivities with other gases. Chlorine compounds such as ClO2 and nitrogen compounds such as NO2 look very much like ozone to many instruments. Strong VOCs such as vapors of alcohols affect most VOC instruments.

Maximum ozone concentration in water varies directly by concentration of the gas in air and inversely by temperature: for example 1.5% feed gas (by weight) will have a maximum concentration of about 11 ppm (mg/L) in water at 5 degrees C and 6.4 ppm at 20 degrees C. Doubling the concentrations of ozone in the feed gas will double the concentration in water.
Dissolved ozone monitors also have cross-sensitivity and other operational problems. For example, the popular and low-cost ORP meters (oxidation-reduction potential meters) are sensitive to pH and various ionic conditions of the water.
Ozone reactions in air are fairly well understood in terms of starting compounds and ending compounds, but the intermediate reactions and compounds are not always well understood.

Ozone reactions in water are generally well-understood and documented, but areas of uncertainty still exist.

Summary of Guidance Notes EH38

UK Health & Safety Executive

Exposure time frame Concentration of ozone ppm
up to a maximum of 8 hours in any one day 0.067
maximum exposure for up to 5 hours per day 0.1
maximum exposure for up to 15 minutes 0.3

note 0.1ppm is approx equal to 0.2mg of ozone per cubic metre of air

The above figures are given as guidance values only

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