Ventilation factor

The test results can be used to predict indoor air levels if load factors, ventilation rates, temperature, air humidity and occupant activities are known. This subject is explained in Chapter 1. By way of example. Figure 2 shows the safe product range that has been established in Sweden for particelboard use in conventional housing (14). As soon as product performance is widely disclosed and builders and architects become familiar with the product ratings, formaldehyde complaints will rapidly decrease and likely become a thing of the past. 

In addition to the previously noted safety factors associated with these processes, there are additional needs for dust control and ventilation for dissipation of various vapors from pressing, tempering/heat treatment, and machining and finishing operations. 

In normal practice, good ventilation to reduce exposure to vapors, splash-proof goggles to avoid eye contact, and protective clothing to avoid skin contact are required for the safe handling of acrylic monomers. A more extensive discussion of these factors should be consulted before handling these monomers (67). 

Options. Traditional control options for overexposure are material substitution, process change, containment, enclosure, isolation, source reduction, ventilation, provide personal protection, change work practices, and improve housekeeping. A simple way of looking at selection of control options is to find the cheapest option that results in the desired amount of exposure reduction. It is not actually that simple, however, because the various options differ in ways other than cost and degree of control. Some of the other factors to consider in selection of control options are operabiUty, rehabiUty, and acceptabihty. 

Health and Safety Factors. Terephthahc acid has a low order of toxicity. Inhalation by rats for 6 h/d, 5 d/wk for 4 wk produced no fatahties at a dust exposure level of 25 mg/m. The mean acute oral toxicity for rats is over 18 g/kg (86), and for mice over 6 g/kg (87). When terephthahc acid was fed as 3% of the diet to rats, urinary calcuh formed in 90 d, some of which led to cancer. High doses of terephthahc acid lead to formation of calcium terephthalate at levels exceeding its solubihty in urine. This insoluble material leads to the calcuh and provides a threshold below which cancer is not observed (88). Normal precautions used in handling industrial chemicals should be observed with terephthahc acid. If ventilation is inadequate, a toxic-dust respirator should be used to avoid prolonged exposure. 

Health and Safety Factors. MSC has a vapor toxicity on mice of LD q 4.7 mg/L. It is a lachrymator and in order to prevent contact with eyes, goggles should be worn. It is also corrosive to skin and therefore chemically resistant gloves and protective clothing should be worn to prevent contact with skin. Containers should only be opened where there is adequate ventilation. 

Butylenes are not toxic. The effect of long-term exposure is not known, hence, they should be handled with care. Reference 96 Hsts air and water pollution factors and biological effects. They are volatile and asphyxiants. Care should be taken to avoid spills because they are extremely flammable. Physical handling requires adequate ventilation to prevent high concentrations of butylenes in the air. Explosive limits in air are 1.6 to 9.7% of butylenes. Their flash points range from —80 to —73° C. Their autoignition is around 324 to 465°C (Table 2). Water and carbon dioxide extinguishers can be used in case of fire. 

The selection of the method used depends on many complex factors, which are not covered in this paper. The basics of each of the two methods are briefly covered. Only a few of these techniques would be used in the water treatment procedure encountered in the industrial ventilation field however, for the sake of completeness others are also covered. 

Vernon, H. M. (1948). An investigation of the factors concerned in the causation of indnstriai accidents. In Baste Principles of Ventilating and Heating. T. Bedford, Lewis Co., p. 346,... 

Ventilation noise originates primarily from fans and the air turbulence generated inside ducts and around supply air and exhaust air terminal devices. The appearance of the noise is, of course, affected by factors such as the speed of rotation and the power of the fan, and by how the fan is stabilized or in other ways acoustically insulated. The noise level and the frequency characteristics are also largely derermined by the velocity of the air inside ducts and around terminal devices, where factors such as the dimensions and appearance of the ducts and terminal devices may play a decisive role in the appearance of the noise. 

The range of answers to the question, How does ventilation noise affect your ability to perform your tasks reveals that about one in every five office workers on average felt that ventilation noise made their work more difficult. A significantly greater number assessed the higher level at 40 dB(A) as an aggravating factor in the performance of their tasks at the office. About 20% considered that the higher level made their work somewhat or much more difficult. About 10% made a similar assessment at the noise level of 35 dB(A). 

The significant differences in disturbance, when evaluated with regard to the average noise levels, shows that the noise level is a decisive factor with regard to disturbance. Measures to limit the disturbance reaction due to ventilation noise should, therefore, naturally be directed in the first instance at lowering the noise level. 

One of the most critical factors is draft. Many people at low activity levels (seated/standing) are very sensitive to air velocities, and therefore draft is a very common cause for occupant complaints in ventilated and air-conditioned spaces. Fluctuations of the air velocity have a significant influence on a person s sensation of draft. The fluctuations may be ex-... 

A summary of essential items to be taken into account in determining the target levels is presented in Table 6.20. The table shows that the process is the main determining factor for industrial ventilation. 

Major factors affecting air and contaminant movement inside ventilated space are summarized in Section 7.3 and can be classified as... 

In some cases, the ventilation process in the room can be simplified and mechanisms of air and contaminant movement under the influence of each of the above factors can be described using simplified theoretical principles of fluid mechanics, empirical data, and observations from numerous research studies. In general, the ventilation process in a room is complex and different factors have a joint effect on airflow patterns and characteristics, in continued spaces and in industrial buildings particularly. 

Airborne contaminant movement in the building depends upon the type of heat and contaminant sources, which can be classified as (1) buoyant (e.g., heat) sources, (2) nonbuoyant (diffusion) sources, and (d) dynamic sources.- With the first type of sources, contaminants move in the space primarily due to the heat energy as buoyant plumes over the heated surfaces. The second type of sources is characterized by cimtaminant diffusion in the room in all directions due to the concentration gradient in all directions (e.g., in the case of emission from painted surfaces). The emission rare in this case is significantly affected by the intensity of the ambient air turbulence and air velocity, dhe third type of sources is characterized by contaminant movement in the space with an air jet (e.g., linear jet over the tank with a push-pull ventilation), or particle flow (e.g., from a grinding wheel). In some cases, the above factors influencing contaminant distribution in the room are combined. 

Another factor influencing contaminant and heat transfer from dirty to clean zones against the stable airflow is a turbulent exchange between these zones. This process should be considered in the design of displacement or natural ventilation systems and evaluation of the emission rate of contaminants from the encapsulated process equipment (Fig. 7.111a). 

The term natural ventilation relates to the airflow in a building that is caused by three natural factors ... 

At least three factors must be considered when using Eq. (10.132). The first is that the room air is seldom well mixed the second is that the emission rate is usually unknown and the third is that measurement of is often very difficult, especially in spaces where a mixture of mechanical and natural ventilation is used. If the room air is poorly mixed, a sampling strategy is needed in order to determine the room air concentration (C,). There exist different strategies for this, and two are as follows ... 

Outdoor air temperature is an important factor regarding the building energy balance. Outdoor air temperature affects the heat transfer through external walls and roofs and the heat transfer by ventilation. Moreover, outdoor air... 

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