Enclosure booths

Provision and use of appropriate health surveillance, e.g. for signs of dermatitis, asthma, effects of specific solvent exposures. Full use of any spray booth, enclosure, exhaust ventilation or dilution systems, and automatic handling equipment. (The efficiency of all local exhaust ventilation and other control systems should be maintained, and checked by testing.) Where appropriate, atmospheric monitoring of airborne pollution levels. 

Partial enclosures are a compromise between containment and access. Most people misunderstand the function of partial enclosures. It is not possible to completely separate the interior from the surroundings with partial enclosures. Complete separation is only possible with total enclosures. The function of a partial enclosure is as dependent on the flow rate, the flow field, the working procedures, the contaminant generation process, etc. as is the function of exterior hoods. The advantage with a partial enclosure is that the physical walls diminish the possibilities for the contaminants to escape from the hood to the surroundings. Thus these hoods could be used when relatively high demands are put on the contaminant concentration outside the hood. Some of the most commonly used enclosures, such as fume cupboards and booths, are described. Many variations of these exist, e.g., enclosure of the complete process, and some of these are described here. 

Booths are partially enclosed workplaces with one or more open facefs) for access by workers. These openings at one or more sides of the enclosure function not only to capture air contaminants directly through their short-distance capture capability but also to cause an airflow in a certain direction (normally away from the worker/work process and into the enclosure). The capture efficiency could be increased by using an existing main flow direction (e.g., thermal flows caused by heat sources) to support the capture process. 

In many processes it is not possible to use enclosures or booths without imposing unacceptable operational restraints (see Figure 46.2). The hood must be placed at some distance from the source. The natural projection of the... 

Full use of any spray booth, enclosure, exhaust ventilation or dilution systems, and automatic handling equipment. Full use, where appropriate, of ventilation, e.g. by opening doors, windows. 

Local exhaust ventilation serves to remove a contaminant near its source of emission into the atmosphere of a workplace. A system normally comprises a hood, ducting which conveys exhausted air and contaminants, a fan, equipment for contaminants collection/ removal and a stack for dispersion of decontaminated air. Hoods normally comprise an enclosure, a booth, a captor hood or a receptor hood. Those relying on other than complete enclosure should be as close a practicable to the source of pollution to achieve maximum efficiency. 

If enclosure or use of a booth is impracticable, a captor hood is used. This is placed some distance from the source of pollution and the rate of air flow needs to be such as to capture contaminants at the furthermost point of origin. 

Minimum Duct Velocity. Once the types and locations of hoods, enclosures and booths have been established and the exhaust rates determined, it is necessary to design the ductwork to transfer the contaminated gas to the collection or cleaning device. An essential parameter required for this purpose is the minimum duct or conveying velocity, Vfmm, which is required to ... 

A modified form of enclosure exists in a paint booth where water is used as the physical barrier. In addition, however, the booth should be curtained off. 

This type of system may be used for the extinguishment of surface fires in flammable liquids, gases, and solids where the hazard is not enclosed. Examples of hazards that may be successfully protected by local application systems include dip tanks, quench tanks, and spray booths. Since local application systems do not utilize enclosures to maintain design concentrations, two methods for determining the quantity of carbon dioxide required for extinguishment are used. These are ... 

The second field test assessed PCO to treat paint solvent vapors. Painting operations for military and civilian vehicles are conducted in ventilated enclosures called paint booths. Filters in the exhaust ducts trap paint droplets from the paint overspray while the VOC-laden air is typically exhausted through roof vents. The vent emissions can contain several hundred parts per million (ppm) of the paint solvents, which continue to evaporate from the vehicle after painting is complete. Most types of paint generally contain significant amounts of VOCs such as toluene, a suspected carcinogen, as well as other hazardous solvents such as methyl efliyl ketone, methyl isobutyl ketone, hexanes, xylenes, n-butyl acetate, and other components in lesser amounts. 

A loss control measure against identified risks by segregating the identified hazard to a specific (remote) location to protect the surrounding area from its effects and vice versa. Examples include placement of a chemical plant or process in a remote location and enclosure of an individual in an acoustic booth or enclosure to protect against noise exposure. 

Mixing, weighing and dispensing operations should be conducted under local exhaust ventilation or in suitable booth enclosures under effective inward airflow conditions, especially if heating or spraying is involved, or when dust from solid isocyanates is generated. 

Dust Control/Explosion Protection Raw material feed systems. For materials which are potential sensitizers, (e.g., enzymes), it is advisable to fully enclose the raw material unloading station and feeder system in a booth with dedicated dust control. This ensures that any release of dust is contained. Operators entering the enclosure should do so with appropriate personal protective equipment. 

Alternate use prohibited. Spray booths, rooms, or other enclosures used for spraying operations shall not alternately be used for the purpose of drying by any arrangement which will cause a material increase in the surface temperature of the spray booth, room, or enclosure. 

Alternate use permitted. Automobile finishing spray booths or enclosures, otherwise installed and maintained in full conformity with this section, may alternately be used for drying with portable electrical infrared drying apparatus when conforming with the following ... 

Acoustic cabins and booths for machine operators or supervisors. Such enclosures should achieve a sound level reduction of between 20 and 30dB and be adequately ventilated air conditioning may also be necessary. They are often of demountable construction, so that they can conveniently be removed and reassembled where and when required. Suppliers of acoustic cabins, etc. are listed in the publication LSI 01-200 (1977). 

The design of worker enclosures requires suitable walls to produce the necessary sound reduction and also some internal sound absorption to prevent reverberant buildup of transmitted sound. The design and location of such booths require careful study and measurement in the field. 

Example If the ACGIH TLV were 20 ppm and the TWA concentration measured were 2000 ppm. the protection factor required would be 100. In fit testing the respirator during quantitative fit testing, the concentration of the air inside the booth, hood or test enclosure is divided by the material measured leaking into the facepiece or enclosure ... 

Ventilation/fiime cupboards - in certain operations (e.g. solvent-based spraying operations or decanting of flammable liquids) booths or cabinets are required to control the build-up of flammable vapours. In such instances the airflow rate into all openings in the enclosure should be sufficient (about 1 m/s) to prevent vapours entering the work area. These ventilation booths, cabinets and other enclosed equipment are generally designed to ensure that the vapours are kept below 25% of their LEL. 

Where the booth is made of steel, the water chamber enclosure for wet or water-wash spray booths shall be 18 gauge or heavier and protect against corrosion. The chamber shall effectively remove particulate matter from the exhaust air stream. 

If the hazard cannot be eliminated, contact might be prevented by using enclosures, machine guards, worker booths or similar devices. 

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