HVAC systems contaminants

HVAC system, contaminant source, and building occupants are present concurrently, the likelihood of an lAQ complaint increases. 

HVAC the HVAC system is not able to control existing air contaminants and ensure thermal comfort (temperature and humidity conditions that are comfortable for most occupants). 

Indoor air contaminants can originate within the building or be drawn in from outdoors. If contaminant sources are not controlled, problems can arise, even if the HVAC system is properly designed and well-maintained. Sources can be from outside the building from operating equipment, from human activities, and other or miscellaneous sources. Sources outside a building include contaminated outdoor air, emissions from nearby sources, soil gas, or moisture or standing water. 

Confirm that the HVAC system maintains appropriate pressure relationships to isolate and contain odors and contaminants in mixed use buildings and around special use areas. Examples of special use areas include attached parking garages, loading docks, print shops, smoking lounges, janitorial closets, storage areas, and kitchens. 

Check the outdoor air intakes to see whether they are located near contaminant sources (e.g., plumbing vents, exhaust outlets, dumpsters, loading docks, or other locations where vehicles idle). See if the space containing the HVAC system is clean and dry. Examples of problems include cleaning or other maintenance supplies... 

An initial walkthrough of the problem area provides information about all four of the basic factors influencing indoor air quality (occupants, HVAC system, pollutant pathways, and contaminant sources). The initial walkthrough may provide enough... 

If the hypothesis or model does not seem to be a good predictor of what is happening in the building, you probably need to collect more information about the occupants, HVAC system, pollutant pathways, or contaminant sources. Under some circumstances, detailed or sophisticated measurements of pollutant concentrations or ventilation quantities may be required. Outside assistance may be needed if repeated efforts fail to produce a successful hypothesis or if the information required calls for instruments and procedures that are not available in-house. Analysis of the information collected during the LAQ investigation could produce any of the following results ... 

Knowledge of the process or operation and contaminant sources is essential before ventilation systems can be selected and designed. Contaminant sources affecting the working environment may be external, associated with the elements of HVAC systems, or internal. 

The HVAC system also acts as a pollutant source when it is not maintained properly. Microorganisms breed in various environments present within components (e.g., cooling coils, ducts) of the system and may be distributed throughout the building. Improper maintenance of filters leads to loss of efficiency and re-emission of contaminants. 

In the current review, the term effectiveness of air distribution will be used to describe the ratio of the occupied zone area (where thermal comfort and contaminant concentration are within ranges required by standards and codes) to the total occupied zone area. This hygienic criterion allows one to judge how well the HVAC system fulfills its main task—creating thermal comfort conditions and controlling contaminants in the occupied zone. 

The vent gas from the ERH flows through an electrically heat-traced duct (to prevent condensation) into an electric heat exchanger that raises its temperature to 260°C (500°F) and then into a CATOX unit to destroy residual organic contaminants. The gas is then cooled to between 12°C and 15°C (60°F) in a scrubber/con-denser that removes additional contaminants. The gas then flows through an induced draft fan, discharging into the plant s HVAC system. 

The amount of agent-contaminated wastes to be disposed of during closure is estimated to be approximately 5.8 million pounds, according to the Facility Closure Plan (Table 1 in the Plan) (U.S. Army, 2000a). This quantity includes (1) waste stored on-site as of April 2000, (2) predicted increases in waste until the end of the munitions campaign (completed November 2000), (3) coprocessing of heavy machinery, (4) USACAP waste inventory, and (5) closure wastes from dismantlement and decontamination primarily in the MDB. Approximately 2.1 million pounds is expected from the dismantlement of the first and second floors of the MDB and the HVAC systems. In addition, approximately... 

The facility should be constructed of materials that facilitate cleaning. Heating, ventilation, and air conditioning (HVAC) systems should be of adequate capacity to produce environmental conditions that comply with employee and animal health and safety standards and should be designed to prevent cross-contamination. 

Heating, ventilation, and air conditioning (HVAC) is a very expensive utility. However, it is essential and serves a variety of purposes. Not only is it important to maintain constant temperature and humidity, it is also important to balance the pressure in the processing areas to minimize cross-contamination opportunities. Dust collection, as mentioned earlier, is very important when handling powders. The dust generated during some processes may be toxic and may pose an explosion hazard. This system is typically very closely associated with the HVAC system. 

HVAC system design influences architectural layouts with regard to items such as airlock positions, doorways and lobbies. The architectural components have an effect on room pressure differential cascades and cross-contamination control. The prevention of contamination and cross-contamination is an essential design consideration of the HVAC system. In view of these critical aspects, the design of the HVAC system should be considered at the concept design stage of a pharmaceutical manufacturing plant. 

Note contaminants may result from inappropriate premises (e.g. poor design, layout or finishing), poor cleaning procedures, contaminants brought in by personnel, and a poor HVAC system. 

Materials for components of an HVAC system should be selected with care so that they do not become the source of contamination. Any component with the potential for liberating particulate or microbial contamination into the air stream should be located upstream of the final filters. 

The systems for fume, dust and effluent control should be designed, installed and operated in such a manner that they do not become possible sources of contamination or cross-contamination, e.g. an exhaust-air discharge point located close to the HVAC system fresh air inlet. 

There are numerous potential locations for filters in an HVAC system. The most common filter placement location is in the mixed airstream within an airhandling unit. Using that location results in filtration of both outside air and return air, and it protects coils and other downstream components from fouling. Filters could also be located directly in the outside airstream, at supply to individual spaces, on the return from individual spaces, in the common return, and on exhaust air (if there is concern about the consequences of contaminated exhaust). Stand-alone filtration devices that recirculate and clean air within a single zone might also be desirable. 

This book describes the interrelationship between HVAC systems and indoor air quality, and includes methods to evaluate an HVAC system as weH as indoor air quality. Pathways of air movement through buildings and sources of air contaminants are also discussed. 

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