| HOSPITAL AIR QUALITY
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 |
3 |
Orthopedic operating room
Bone marrow transplant operating room
Organ transplant operating room |
25 |
90 |
99.97 |
2 |
General procedure operating rooms
Delivery rooms
Nurseries
Intensive care units
Patient care rooms
Treatment rooms
Diagnostic and related areas |
25 |
90 |
|
1 |
Laboratories
Sterile storage |
80 |
|
|
1 |
Food preparation areas
Laundries
Administrative areas
Bulk storage
Soiled holding areas |
25 |
|
|
|
|
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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