ozone

A mass balance model is used to examine the impact of two ventilation (1 /h and 2 /h) and recirculation (7 /h and 14 /h) rates on concentrations, exposure to and intake of ozone (of outdoor origin) and secondary organic aerosols (SOA) derived from the ozone initiated chemistry in indoor environment. Measured data from several experimental studies conducted by the authors in a 236m3 field environmental chamber (FEC) configured to simulate an office are used for the mass balance model evaluations.

The concentrations of ozone, particles (PM10 and PM2.5) and ultra-fine particles were measured duringdriving the automobile and during standing. Two ventilation modes were prepared; 1) all fresh air modeand 2) all re-circulation mode. The windows of the automobile had been always closed during thismeasurement. The indoor/outdoor ratio of the concentrations and the correlation among thosesubstances were reported. The concentrations of particles (PM10 and PM2.5) and ultra-fine particleswere dramatically had been increased while the automobile followed the trailer bus.

Decomposition of toluene in air was studied by dielectric barrier discharge (DBD) on the one hand aswell as UV light as assistance to DBD on the other hand.Input energy to reaction chamber, flow rate of contaminated air, and concentration of toluene werestudied as parameters influencing on the decomposition rate of toluene by two methods.Increasing the input energy from 2.8 kV to 4.2 kV at flow rate 1 SLM was increased the decompositionrate of toluene from 3.5% to 10%.

Indoor ozone has received attention because of its well-documented adverse effects on health. Inaddition to the inherently harmful effects of ozone, it can also initiate a series of reactions that generatepotentially irritating oxidation products, including free radicals, aldehydes, organic acids and secondaryorganic aerosols (SOA). The overarching goal of this work was to better understand ozone and terpenedistributions within rooms. Towards this end, the paper has two parts.

Gas phase filters have been installed within the air handling unit of an HVAC system feeding 100 %fresh (outdoor) air to an office building. The filters efficiency for ozone (O3) and nitrogen oxides (NO2and NO) has been measured continuously over a one year period as function of time and outdoor airparameters (temperature, relative humidity). The results show that the filters efficiency varies alongtime and depends on temperature and relative humidity of air.

That study provides data on compared outdoor and indoor concentration levels of ozone and nitrogen oxides in 8 school buildings in France. It also gives information on the parameters that influence the relationship between outdoor and indoor air quality (such as indoor humidity, indoor temperature, building occupancy, airthightness of the building envelope). Results and discussion are presented.

This paper reports the results of room model experiments and Computational Fluid Dynamics(CFD) analysis of ozone distribution in indoor air. The analyzed room model had one supply inlet and one exhaust outlet, with a cavity of dimensions 1.5m (x) 0.3m (y) 1.0m (z) in which a two-dimensional flow field was developed. In order to discuss the order of wall surface deposition for ozone, the concentration distributions of ozone in the model room were measured. CFD analysis corresponding to the experimental conditions and with a built-in ozone wall surface deposition model was carried out.

That study was conducted in Nashville (TN) : during six weeks, measurements using passive ozone samplers were made on a group of school children aged 10 to 12 to estimate the outdoor/indoor /personal ozone exposure. Personal ozone exposure depends of the time spent indoors and outdoors.

Ozone concentrations were monitored up- and downstream of used filter samples at airflowsof 1.0 and 0.2 l s-1. The ozone concentration in the air upstream of the filters was ~75 ppb,while the concentration downstream of the filter was initially ~35% lower at 1 l s-1 and ~55%lower at 0.2 l s- 1. Within an hour the removal efficiency had decreased to roughly 5% at1 l s- 1 and 10% at 0.2 l s- 1. These filter samples were then placed in either nitrogen or ambientair for 48 h. Afterwards it was found that there was partial regeneration of the filters ozoneremoval capabilities.

Ultra-fine and fine particle formation as a result of chemical reactions between ozone and fourdifferent air fresheners and a typical lemon-scented domestic cleaner was studied in a fullyfurnished, naturally ventilated office. The study showed that under conditions representativeof those occurring in such offices, air fresheners or scented cleaners may react with ozone toform secondary organic aerosols (SOA). The tested air fresheners were relatively smallsources of SOA with detectable increases occurring only in the ultra-fine particle numberconcentration.