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 C1O2 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.
Ozone in Air (High
concentrations such as the outputs of corona discharge generators)
(Concentrations
by Weight)
(10) 1 g O3/m³ = 782 ppm
by weight
(11) 100 g O3/m³ = 7.82$
O3 in air
(12) 1 % O3 (by weight)
= 12.8 g/m³ in air
(13) Conc. by weight G (or
w/w) = c x .29 x T/P = 0.782C at STP
C = Conc. in G/M³
Ozone in Oxygen
(High
concentrations by Weight)
(14) 1 g O3 /m³ (of O2)
= 699 ppm by weight
(15) 100 g O3 /m³ (of
O2) = 6.99% of O3 in O2
(16) 1% O3 (by weight)
= 14.3 g/m³ in oxygen
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 (bei weight)
Standard Temperature and
Pressure
273.3 K (O° C, 32° F) and
1013.25 mb (14.706 psi)
Metric Volume and Length
(1) 1 m³ = 1.000 liters
(2) 1 g/m³ = 1 mg/L = 1
ppm ozone (by weight) in water
(3) 1 foot = .305 meter
1 meter = 3.28 feet
(4) 1ft³ = .0283 m³ 1 m³
= 35.3 ft³
Ozone in Water
(5) 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)
(6) 1 g O3/m³ = 467 ppm
by volume
(7) 1 ppm O3 (volume) =
2.14 mg O3/m³
(8) 1 ppm O3 (volume) =
214 ug/m³ (used more often in Europe)
(9) Concentration by volume,
v/v = C (g/m³) x 1733 x T/P = 467C at STP
