Ozone relative humidity

A diagram of a typical gas-phase (ozone-ethylene) chemiluminescent ozone analyzer is shown in Figure 6-10. The detector responds linearly to ozone concentrations between 0.003 and 30 ppm no interferences were initially observed. More recently, however, it has been established that, as the relative humidity goes from 0 to 60% and the temperature from 20° to 25° C, water vapor produces a small positive signal that results in an increase of about 8% in the ozone concentration measurement. This potential source of error can be minimized by using humidified, rather than dry, ozone in air streams when calibrating. 

Kagawa and Toyama in Tokyo followed 20 normal 11-yr-old school children once a week from June to December 1972 with a battery of pulmonary-function tests. Environmental factors studied included oxidant, ozone, hydrocarbon, nitric oxide, nitrogen dioxide, sulfur dioxide, particles, temperature, and relative humidity. Temperature was found to be the most important environmental factor affecting respiratory tests. The observers noted that pulmonary-function tests of the upper airway were more susceptible to increased temperature than those of the lower airway. Although the effect of temperature was the most marked, ozone concentration was significantly associated with airway resistance and specific airway conductance. Increased ozone concentrations usually occur at the same time as increased temperature, so their relative contributions could not be determined. 

Only metabolites leached from the cell were affected. Elford and van den Ende reported that ozone at 20 ppm had a lethal effect on some bacteria deposited from aerosol mists on various surfaces. Relative humidity is an important factor, particularly when ozone concentration is low. They found little death at a humidity below 45%, at concentrations of 1 ppm, as opposed to a 90% kill in 30 min at 0.025 ppm with a humidity of around 70%. A 5-min exposure of Bacillus cereus to ozone at 0.12 mg/liter was the minimal lethal dose, whereas 0.10 mg/liter was effective for B. megaterium and E. coli. Spores of the Bacillus sp. were killed by ozone at 2.29 mg/liter. These responses were of the all-or-none type with ozone between 0.4 and 0.5 mg/liter of water. Time of exposure, from 1 to 32 min, was not important. Chlorine was effective at 0.27-0.30 mg/liter, with time an important consideration. These two gases did not affect E. coli in the same way. 

However, as discussed by Reiss et al. (1995a), separating the contribution of ozone reactions from other factors such as temperature and relative humidity, which also affect direct emissions, is difficult. For example, while the production rate of oxygenated organics is correlated with the ozone removal rate, the latter is also correlated with temperature. As a result, both reaction and increased direct emission rates due to higher temperatures may be contributing to these enhanced indoor levels. 

The monthly mean ozone from the Dobson time series (1957-1986) of Vigna di Valle (50 km apart from Rome) and from TOMS (Total Ozone Mapping Spectrometer) satellite data (1979-1991) version 6 are assumed as climatological frames of reference for Rome and Ispra, respectively. Aerosol optical depths at 550 nm are estimated by means of sunphotometry. Data from the two meteorological stations of Rome and Milan airports are used to describe the atmospheric conditions. Standard vertical profiles of pressure, temperature, relative humidity and ozone density are selected. 

Upper airway irritation of terpene/ozone oxidation products (TOPS). Dependence on reaction time, relative humidity and initial ozone concentration. Toxicology Letters, 143 (2), 109-14. 

Similarly, the relative humidity has a strong influence on the chemical composition of the secondary organic aerosol formed in the atmosphere by the reaction of ozone with 1-tetradecene <2000EST2116> thermal desorption particle beam mass spectrometric determinations found that the main products are a-hydroxytridecyl hydroperoxide and a peroxy-hemiaceta 1. 

This is of paramount importance, and in conservation terms there can be no better investment. An air-conditioning unit should be installed which will provide book-stack temperatures of 60°-65°F with a relative humidity of 45-60%. Below this range, embrittlement of materials will occur, and covers may warp above it, the growth of mold is encouraged. Deterioration of book materials is minimized when the temperature and the relative humidity are constant. The system should water-wash air free of sulfur dioxide, which is the most effective purifying method available, and it should eliminate ozone (1). 

Palluau, F., Mirabel, P., Millet, M. Influence of relative humidity and ozone on the sampling of volatile organic compounds on carbofrap/carbosieve adsorbents. Environ. Monit. Assess. 127, 177-187 (2007)... 

Generating Aerosols by Dark Phase Ozone Reaction. Reactants, various hydrocarbons and O3, were brought together in low ppm or tenths of a ppm concentration in 150-liter Teflon bags. The organic reactants used were a-pinene, cyclohexene, 1,5-hexadiene, cyclohexane, and 2-hexene. In all but one series of experiments, relative humidity was virtually zero (dew point <—48°C). In experiments using cyclohexene and O3, the water vapor pressure was varied relative humidities of -. 0%, — 50%, and 95-100% were used at 21°C. a-Pinene and other hydrocarbons alone in clean air in Teflon bags do not deteriorate detectably in 24 hours ozone deteriorates less than 5% in 18 hours. 

The complete data on the l-butene-NOa system (see Table II) are scattered because of the varying l-butene NO ratios in these runs, but certain trends are apparent. Adding CO decreased the time required to reach the NO2 maximum concentration and the half-life of the 1-butene. Also the amount of O3 produced seemed to increase with increasing CO concentration. The data also show that adding water vapor decreased the peak ozone concentration this result agrees with the results of Wilson and Levy (13) who also observed that less ozone was produced by irradiating 1-butene with NO. at higher relative humidities. 

The concentration of ozone in such tenderizing rooms, according to Ewell (11, 12), is of the order of 0.1 p.p.m. by volume. Elford and Van den Ende (6) have shown that ozone as low as 0.04 p.p.m. can destroy bacteria if the relative humidity is 60 to 90%. Mallmann and Churchill (20), experimenting with naturally contaminated beef, also showed that 0.1 p.p.m. by volume of ozone would retard the growth of the organisms. 

The Sterilamp ultraviolet tube producing a minute amount of ozone has been used to destroy mold on Cheddar cheese during ripening 13, 14). Ewell (11) has reported that less than 0.2 p.p.m. by volume will extend the holding time by 11 weeks at 69° F. and 80 to 85% relative humidity before the appearance of visible mold on the cheese. The ozone also oxidized the odor in the room. 

The primary purpose of the Sterilamp tube in air-conditioning systems has been to destroy microorganisms (22). Tests on the effect of 1 to 2 p.p.m. by voliune of ozone on E. coli sprayed into an air duct revealed that the organisms were not destroyed. This would confirm the data of Elford and Van den Ende ( ) that ozone is a poor disinfectant of air at low relative humidity. At high relative humidity these authors found that as low as 0.04 p.p.m. by volume destroyed bacteria dispersed in an aerosol. This would also agree with the results reported here, that organisms on surfaces and seeded on Petri plates can be destroyed by minute amounts of ozone. 

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