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Glass &Windows Selection


Systems must also provide air virtually free of dust, dirt, odor, and chemical and radioactive pollutants. In some cases, outside air is hazardous to patients suffering from cardiopulmonary, respiratory, or pulmonary conditions. In such instances, systems that
intermittently provide maximum allowable recirculated air should be considered.

Outdoor Intakes.

These intakes should be located as far as practical (on directionally different exposures whenever possible), but not less than 30 ft, from combustion equipment stack exhaust outlets, ventilation exhaust outlets from the hospital or adjoining buildings, medical-surgical vacuum systems, cooling towers, plumbing vent stacks, smoke control exhaust outlets, and areas that may collect vehicular exhaust and other noxious fumes. The bottom of outdoor air intakes serving central systems should be located as high as practical (12 ft recommended) but not less than 6 ft above ground level or, if installed above the roof, 3 ft above the roof level.

Exhaust Outlets.

These exhausts should be located a minimum of 10 ft above ground level and away from doors, occupied areas, and operable windows. Preferred location for exhaust outlets is at roof level projecting upward or horizontally away from outdoor intakes. Care must be taken in locating highly contaminated exhausts (e.g., from engines, fume hoods, biological safety cabinets, kitchen hoods, and paint booths). Prevailing winds, adjacent
buildings, and discharge velocities must be taken into account In critical or complicated applications, wind tunnel studies or computer modeling may be appropriate.

Air Filters.

A number of methods are available for determining the efficiency of filters in removing particulates from an airstream . All central ventilation or air-conditioning systems should be equipped with filters having efficiencies no lower than those indicated in below Table


Filter Efficiencies for Central Ventilation and Air-Conditioning Systems in General Hospitals
Filter Efficiency %
Minimum Number of Filter Beds Area Designation Filter Bed 1 Filter Bed 2 Filter Bed 3

Orthopedic operating room

Bone marrow transplant operating room

Organ transplant operating room


General procedure operating rooms

Delivery rooms
Intensive care units
Patient care rooms
Treatment rooms
Diagnostic and related areas


Sterile storage
Food preparation areas

Administrative areas
Bulk storage
Soiled holding areas

Where two filter beds are indicated, Filter Bed No. 1 should be located upstream of the air-conditioning equipment, and Filter Bed No. 2 should be downstream of the supply fan, any recirculating spray water systems, and water-reservoir type humidifiers. Appropriate precautions should be observed to prevent wetting of the filter media by free moisture from humidifiers.
Where only one filter bed is indicated, it should be located upstream of the air-conditioning equipment. The following are guidelines for filter installations:
1. HEPA filters having DOP test efficiencies of 99.97% should be used on air supplies serving rooms for clinical treatment of patients with a high susceptibility to infection due to leukemia, burns, bone marrow transplant, organ transplant, or human immunodeficiency virus (HIV). HEPA filters should also be used on the discharge air from fume hoods or safety cabinets in which infectious or highly radioactive materials are processed.
The filter system should be designed and equipped to permit safe removal, disposal, and replacement of contaminated filters.

2. All filters should be installed to prevent leakage between the filter segments and between the filter bed and its supporting frame.
A small leak that permits any contaminated air to escape through the filter can destroy the usefulness of the best air cleaner.

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