Directional airflow

The design criterion of the piston strategy is to overcome all the air currents opposite to the directional airflow created within the room. 

Some new features of furnaces available today include variable speed blowers, which deliver warm air more slowly and more quietly when less heat is needed, and variable heat output from the burner, which when combined with the variable speed blower allows for more continuous heating than the typical fixed firing rate. Distribution system features can be sophisticated with zoned heating which employs a number of thermostats, a sophisticated central controller, and a series of valves or dampers that direct airflow or water to different parts of the home only when needed in those areas. 

Directional airflow based on pressure differential is noted along with special exhaust requirements. 

Airflows Prevent migration of contaminants into uncontrolled areas through use of directional airflows. Separate/dedicated work areas required... 

A dunk tank or attached decontamination air lock system may be used to introduce or remove material from the Class III system. Figure 8. All primary containment devices shall be certified to meet performance criteria on initial installation, following any move or maintenance, and at least annually. Other safety features of facility design include nonporous surfaces on floors, walls, and ceiling self-closing doors that must remain closed to maintain air balance and directional airflows. If floor drains are present, their traps should be filled with water weekly. 

The particular feature of Gonidur sheets is the specific hole shape which creates a directional airflow to help in discharging the product and to influence the retention time in the fluid bed. The special method of manufacturing Gonidur sheets enables finishing of fine perforations in sheets with an initial thickness many times over the hole width. Perforations of only 100 pm in an initial sheet thickness of 0.7 mm are possible. With holes this small 1 m of plate may comprise several hundred thousand individual orifices. 

Directional airflow within production or packing areas should assist in preventing contamination. Airflows should be planned in conjunction with operator locations, so as to minimize contamination of the product by the operator and also to protect the operator from dust inhalation. 

Point extraction alone is usually not sufficient to capture all of the contaminants, and general directional airflow should be used to assist in removing dust and vapours from the room. 

Fig. 10.13 Three alternative air flows which are possible in the polygonal drum of one supplier (courtesy Driam, Eriskirch/ Bodensee, Germany), (a) Reverse air flow from the bottom through the particle bed with air exhaust at the top (b) direct airflow from the top through the particle bed with air exhaust at the bottom (c) axial reverse flow from the bottom through the particle bed with air exhausting through the hollow shaft.

Figure 76 Wall mounted duct directing airflow across the width or down the sidewall of the room.

The collection media in this type of filter can be composed of various materials including hair, spun glass, wool, paper and asbestos. (In the past, asbestos has been used in the manufacturing of all types of filters. Since asbestos is cancer causing, be sure to specify a non-asbestos fiber). The ex-Tended surface media filter consists of folds of material woven back and forth. Corrogated aluminum or paper separators are inserted perpendicularly to the filter face and separate the folds to help direct airflow in an even, parallel fashion. 

A ducted exhaust air ventilation system is to be provided. The system is to be designed so as to create directional airflow that draws air from clean areas into the laboratory toward contaminated areas. The exhaust air is notto be recirculated to any other area of the building, and is to be discharged to the outside with filtration and other treatment as needed. The outside exhaust must be dispersed away from occupied areas and air intakes. Laboratory personnel must verify that the direction of the airflow (into the laboratory) is proper (a static pressure gauge with an alarm between the laboratory and... 

A dedicated nonrecirculating ventilation system is to be provided. The supply and exhaust components of the system are to be balanced to assure directional airflow from the area of least hazard to the areas of greatest potential hazard. The differential pressure/directional airflow between adjacent areas is to be monitored and alarmed to indicate malfunction of the system. The airflow in the supply and exhaust components is to be monitored and the components interlocked to assure inward (or zero) airflow is maintained. 

A non-recirculating ventilation systemis provided.The supply andexhaustcom-ponents ofthe system are balanced to provide for directional flow of air into the animalroom. The exhaustairis discharged directly to the outside and clearofoccupiedareas and air intakes. Exhaust air from the room can be discharged without filtration or other treatment. Personnel must periodically validate that proper directional airflow is maintained. 

A ventilation system fan sequencing interlock ensures that Zone 1 confinement boundary integrity is not compromised by either exhaust fan faiiures or operational errors. This interlock automatically starts the backup exhaust fan if the operating exhaust fan fails, thereby maintaining the desired directional airflow control across ventilation exhaust system boundaries. Thus, no operator action is required to maintain Zone 1-to-Zone 2A differential pressure in the event of exhaust fan failures. 

Some BSCs are exhausted through canopy units (also called thimble units). Figure 7.3.4.3 shows a canopy unit. This unit is not directly connected to the BSC but rather is placed in close proximity to the exhaust. There is about an inch of space between the BSC exhaust pipe and the inside lower lip of the canopy unit. The canopy unit serves two purposes it removes any volatile chemical vapors that might be exhausted from the BSC or in the laboratory and it provides a source of ventilation for the laboratory room especially when the BSC is off, thus preserving the directional airflow into the laboratory. 

Tertiary containment describes the use of a defined operational facility to prevent contamination of the environment external to the laboratory or production area. This is achieved by facility design (e.g. directional airflows and air filtration), effluent treatment and operational procedures. 

Engine components. Parts fabricated from injection-molded fiber-reinforced polyamide-imides provide a lower-cost solution to previously machined metal pieces and maintain, due to low shrinkage, very tight tolerances which are required in these applications. Polyamide-imide compounds have replaced expensive titanium in air return grills for commercial aircraft engines (Fig. 12.13). The shroud on the interior of the aircraft engine, responsible for directing airflow, consists of an assembly of multiple polyamide-imide injection-molded pieces (Fig. 12.14). 

Cooling towers—devices used by industry to remove heat from water. In a typical tower, a boxshaped collection of multilayered slats and louvers directs airflow and breaks up water as it cascades from the top of the water distribution system. Cooling towers are classified by the way they produce airflow and by the way the air moves in relation to the downward flow of water. Basic designs include atmospheric, natural, forced, and induced draft. 

A cooling tower is a large rectangular or box-shaped device filled with wooden or plastic slats and louvers that direct airflow and break up water as it falls from the top of the water distribution header. The internal design of the tower ensures good air and water contact. 

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