Exhaust Vents

FIGURE 7.105 Schematics of naturally ventilated space /, air inlet 2, exhaust vents. 

Wilson, D. J. 1976. Combination of air intakes from roof exhaust vents. ASHR.AFi Transactions, vol. 82, pp. 1024-1038. 

Typical industry practice is to provide an explosionproof rated exhaust fan in the exhaust system for the battery room and classify the exhaust duct and a radius of 1.5 meters (5 ft.) from the exhaust vent outlet at Div. I, Class 2 Group B. The light switch for the facility should be located outside the battery room. 

Most enclosures are provided with a high interior air cooling flow that is also helpful to disperse any gas release. Combustible gas detection is provided in the interior of the enclosure and at the air exhaust vent. Fixed temperature devices are also installed. 

The tube is connected to the top of the reflux condenser and attached to a length of tygon tubing. The end of the tubing is positioned in the exhaust vent of the hood to remove any hydrogen cyanide vapor. 

Safe havens may be rare on some sites however, many buildings can provide personnel with temporary protection until the incident has been analyzed and a decision made on the need for evacuation. To qualify as a designated temporary safe haven, a building must be reasonably well sealed against air infiltration, with adjustable ventilation systems that can reduce or close off exhaust vents and outside makeup air. Emergency procedures should state how long a building can be considered a safe haven under specified exposure conditions. 

After the air stream left these traps, It passed through about 10 ml of CCl where the bromine remained, and from there through some traps to a vacuum pump, and then to an exhaust vent of the room. The CCl could be maintained at a nearly constant level by connection to a large reservoir. 

This incident was the first chemical terrorist attack in a large city. There were few first responders who could even have conceived of such an attack and would have been prepared to rapidly evacuate victims from the subway station premises. Many passengers who had difficulty walking rushed out of the trains and onto the subway platform and fell down, which in effect would have increased their exposure to sarin in the subway station. In addition, the site to which many of the victims were finally evacuated at ground level where they could lie down was in close proximity to an air exhaust vent from the subway below. 

In the casting mold exhaust vents are arranged opposite the inlet casting vents. They measure 0.03 mm in depth and 3-12 mm in width and are intended to enable the withdrawal of volatiles. 

Ventilation is an important method of reducing the level of toxic airborne contaminants in the process environment. Ventilation includes general (dilution) ventilation and local exhaust (vent) ventilation. General ventilation involves dilution of air and hence the term dilution ventilation. Local exhaust ventilation is a method of removing contaminants before they enter the workplace air. Local ventilation is typically achieved by employing a hood that covers the specific area of contamination. 

In a 1-1. three-necked round-bottomed flask equipped with a 50-ml. buret, a 500-ml. graduated dropping funnel, a thermometer, a stirrer, and an exhaust vent protected with a soda-lime drying tube, is placed 378.4 g. (2.22 mols) of bis(dimethylamido)phosphoryl chloride (synthesis 21). In the buret there is placed 20 ml. (1.11 mols) of water, in the graduated dropping funnel is added 232.0 g. (2.30 mols) of triethylamine, and the volume (approximately 320 ml.) is recorded. The contents of the reaction flask are heated to 45 to 50° and then the heater is removed. One milliliter of water is added, followed by one-twentieth (approximately 16 ml.) of the triethylamine. The reaction mixture is stirred until the mildly exothermic reaction subsides (ca. 5 minutes), and the addition of 1 ml. of water followed by... 

Exhaust vents are designed to relieve overpressure within the growing room caused by the introduction of fresh air. Without an exit for the air, a back pressure is created that increases resistance and reduces the CFM of the fan. Small rooms operating with low fresh air requirements can forgo special exhaust vents and allow the air to escape around the seals of the room entrance, in effect creating a positive pressure environment. Positive pressure within a room can also be created by... 

Fresh air intakes and exhaust vents must be screened with fine mosquito netting. Be sure there are no cracks around the filters and fan housing. 

The moving spiral (red) pushes a pocket of evacuated air through the spiral pathway thereby compressing the air until it escapes through the central exhaust vent. 

In the batch process, it typically takes a day or two to load a typical-size concrete kiln with about 50 cords of wood. When the fire is started, air intake ports and exhaust vents are fully open to draw in enough oxygen to produce a hot fire. During the week-long burning period, ports and vents are adjusted to maintain a temperature between abont 450°C-510°C (840 F-950°F). At the end of the... 

The batch process for charring wood produces significant amonnts of particnlate-laden smoke. Fitting the exhaust vents with afterburners can reduce the emissions by as mnch as 85%, but because of the relatively high cost of the treatment, it is not commonly used. 

Fig. 4.6 The NBS chamber of ASTM E 662-79 1 photomultiplier tube housing 2 chamber 3 inlet vent damper 4 exhaust vent damper 5 optical system rods 6 optical system floor window 7 photometer, 8 base cabinet 9 door with window 10 blow-out panel. Copyright ASTM. See footnote of Fig. 3.21...

Installing or upgrading main or auxiliary ventilation systems, such as tailpipe or stack exhaust vents to capture and remove emissions in maintenance shops or other indoor locations. 

Even without the presence of chemical hoods (which necessarily remove air from the lab) there will be HVAC inlets and exhaust vents in the lab. There is no OSHA standard on the turnover rate in labs, although a value of six is considered a reasonable rate. At this rate, assuming complete mixing, about 98% of the air is replaced in 1 hour. Since it is reasonable to expect that some chemical vapors may occasionally be present in a lab (although prudent use of a chemical hood should virtually eliminate this), a reasonable turnover rate should maintain a healthy atmosphere. 

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