Ventilation rate measurement

Capture efficiency can also be measured by first estimating workspace emission rates and local exhaust emissions. The local exhaust emission rate equals the duct concentration (mass/volume) multiplied by the duct flow rate (volume/time). The workspace emission rates can be calculated using appropriate mass balance models and measured ventilation rates and workspace concentrations. Capture efficiency is the ratio of duct emission rate to total emission rate (duct plus workspace). ... 

Figure 12.42 shows another example of the use of similarity principles in experiments. The temperature effectiveness ej is measured in a room ventilated by displacement ventilation. The measurements are made at different flow rates to the room, at different loads (from 100 W to 500 W) and by... 

The starting point for design of a dilution ventilation scheme is normally a hygiene survey in which levels of pollutants and the ventilation rate are measured under worst conditions. The required ventilation rate is then calculated by ratio of level of contamination measured and required, where... 

Here we have only discussed the concentration of the radon gas. This is because the measurements have been made of this nuclide. However, the health effects are referred to the short-lived decay products. The equilibrium factor depends on the ventilation rate and the particle concentrations. 

The radon emanation and the ventilation rate of a room can be derived from the increase of the radon concentration by the radon exhalation and from the steady state condition between exhalation and air exchange with the free atmosphere. In Fig. 2 the variation of the radon concentration as function of time is shown measured in two houses with different radon emanations and ventilation rates. 

In a certain period of time there is a steady state condition in a room and a constant radon activity concentration cj(°°) could be measured. By means of this value and equations (2) (with t = 00) and (3) the actual ventilation rate of a room can be calculated ... 

The rooms without aerosol sources and low ventilation rate (v<0.3 hf1 ) had low aerosol concentrations (2 103 - 104 cm-3) due to the small influence of the higher aerosol concentrations outdoors (aerosols by traffic and combustions) (Table la). In this case the aerosol in the room air was aged by coagulation and plateout and had less condensation nuclei of smaller sizes (d<100 nm). Rooms with a moderate ventilation show higher particle concentrations ((1-5) 10 cm 3) (Table Ila). With aerosol sources in a room (Table III) the aerosol concentrations can increase to 5 105 particles/cm3. The relative error of the measured particle concentration is in the order of 15% primary determined by the uncertainties of the absolute calibrations of the condensation nuclei counter. 

Simultaneous measurements of the radon daughter concentrations, the ventilation rate and the size distribution of the inactive aerosol have been performed in two bedrooms, a living room and a cellar. The measured radon daughter concentrations were fitted by the room model to optimize the deposition rate of the unattached daughters. The mean value was 18/h in the rooms and 8/h in the cellar. 

Together with the radon daughter measurements, nearly continuous measurements of the ventilation rate are performed by means of the release of N2O tracer gas and observation of its decay with an infrared spectrometer (Miran 101). Furthermore the aerosol concentration and size distribution are monitored every 20 to 30 min with an automated aerosol spectrometer (Raes et al.,1984). 

The measurements were performed at four different locations with radon concentrations ranging from 7 to 111 Bq/nr and with low to moderate ventilation rates. The main characteristics of the locations are listed in Table I. 

On this basis the ventilation rate was fitted to the data at high attachment rates and compared to the measured ventilation rate so that the ratio of the "outroom" to the "inroom" daughter concentration (P) could be calculated (Table III). Afterwards the deposition rate of the unattached daughters was calculated from the... 

In Figure 8 the doses per unit radon concentration are plotted as a function of the measured ventilation rate. The NEA conversion factor for low and moderate ventilation (NEA,1983, table 2.10) is multiplied by the appropriate equilibrium factor. In the figure no influence of the ventilation rate on the doses is found. 

Figure 8. Effective dose equivalent per hour and per unit radon concentration (A J B, V J-E) versus ventilation rate. The NEA conversion factor is multiplied by the mean equilibrium factor of the measurements indicated in the ventilation interval.

Initial studies of the indoor concentrations of radon and its decay products were carried out with all exterior doors and windows closed, but with all internal doors fully opened. The radon production rate for the whole house was determined by measuring the 218Po concentration in indoor air and in the air outside the dwelling and by determining the ventilation rate. The radon production rate, K, is given by (Cliff, 1978b) ... 

Ventilation rate was only measured in the sitting room, but the mechanical ventilation system was balanced to provide approximately equal ventilation rates for all areas served by the system. 

Commonly odour samples are taken in the morning, process conditions noted, and air flow rates, temperatures etc measured, followed in the afternoon by the odour strength measuring session. Odour strengths can vary greatly with process conditions, ventilation rates and production procedures and each sample is essentially only a snapshot picture . Therefore even with a rapid method of odour assessment, the total number of odour samples may be no more than the acceptable minimum required to investigate a particular factory or farming situation... 

Radon (222Rn) is formed by the radioactive decay of uranium, BKU (Fig. 15.1a). As a result, the highest concentrations tend to be associated with soils derived from rocks with a high uranium content (Nazaroff and Nero, 1988 Boyle, 1988 Nero, 1989 Mose and Mushrush, 1997). Because radon is a gas that diffuses out of the soil, it can enter homes through cracks in the foundation, around loose-fitting pipes and wall joints, and through floor drains (e.g., Nero, 1989). The concentrations found in a home depend on the type of soil (including the moisture content) on which it sits and the extent of Rn penetration into the house. They also depend on the house ventilation rate and the particular location in the house in which the measurement is... 

In Sweden thermal desorption tubes containing Tenax TA were used to measure VOCs in 178 randomly selected dwellings using a 30 day exposure period (Borne-hag and Stridh, 2000). More than 100 VOCs were identified with a mean concentration less than 25pgm 3. Temperature and ventilation rate were not correlated with VOC concentrations, but there was a correlation with relative humidity to some extent. 

Photo-acoustic Field Gas Monitor 1312 is a gas monitor based on PAS which is accurate, reliable and quantitatively stable. It can be used for on-line concentration monitoring of up to 5 components plus water vapor in gas mixtures. It can also be used to measure the ventilation rate by using tracer-gas and so on (INNOVA Air Tech., 1997). 

Indoor air quality is an important determinant of health and well-being. To maintain better indoor air quality, we have to understand the mechanism of indoor air pollution. For this purpose, the measurement of indoor air concentration and use of chemical analysis methods are essential. To estimate indoor air concentration, we have to know the emission and ventilation rates. Emission takes place not only from building products but also from automobile parts, electric appliances, office equipment such as printers, household consumer products, and even printed materials like newspapers. This book serves as a useful guide for chemists, architects, mechanical engineers, constructors, and manufacturers of electronic products. It emphasizes a holistic and multidisciplinary approach toward the indoor environment. 

Viau 2005). Indeed, such factors as varying ventilation rates associated with varying workloads and dermal exposure are unaccounted for by the air measurement this might make the biomarker a better metric of the actual exposure than the air-concentration measurement of the parent chemical. 

Chamberlain Dyson (1956) measured deposition of unattached 212Pb in a rubber model of the trachea and main bronchi. At an inspiratory flow of 20 1 min-1, corresponding to a ventilation rate of about 0.6 m3 h-1, the activity deposited per cm2 of surface in the bronchi was 0.18% of that entering the trachea. No difference was found in the deposition of unattached 218Po (RaA) compared with unattached 212Pb (ThB). 

In addition to fair, ventilation rates are periodically measured, recorded and maintained at approved levels The majority of workers instructed concerning skin-irritating materials. Workers provided with approved personal protective equipment or devices. Use of this equipment is enforced... 

A student was sent to a house (volume -= 21,000 ft3) to measure the ventilation rate of the house. She quickly added enough SF6 (a nontoxic, inert gas) to the indoor air to bring its concentration up to 100 ppb. She then measured the concentration of this compound every 6 min for about 5h. The results are shown below. How many air exchanges per hour does this house have What happened at point A ... 

A physiologically based pharmacokinetics (PBPK) model based on the ventilation rate, cardiac output, tissue blood flow rates, and volumes as well as measured tissue/air and blood/air partition coefficients has been developed (Medinsky et al. 1989a Travis et al. 1990). Experimentally determined data and model simulations indicated that during and after 6 hours of inhalation exposure to benzene, mice metabolized benzene more efficiently than rats (Medinsky et al. 1989a). After oral exposure, mice and rats appeared to metabolize benzene similarly up to oral doses of 50 mg/kg, above which rats metabolized more benzene than did mice on a per kg body weight basis (Medinsky et al. 1989b). This model may be able to predict the human response based on animal data. Benzene metabolism followed Michaelis-Menton kinetics in vivo primarily in the liver, and to a lesser extent in the bone marrow. Additional information on PBPK modeling is presented in Section 2.3.5. 

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