Surgery and Critical Care
No area of the hospital requires more careful control of
the aseptic condition of the environment than does the surgical
suite. The systems serving the operating rooms, including
cystoscopic and fracture rooms, require careful design to
reduce to a minimum the concentration of airborne organisms.
The greatest amount of the bacteria found in the operating
room comes from the surgical team and is a result of their
activities during surgery. During an operation, most members
of the surgical team are in the vicinity of the operating
table, creating the undesirable situation of concentrating
contamination in this highly sensitive area.
Studies of operating-room air distribution devices and
observation of installations in industrial clean rooms indicate
that delivery of the air from the ceiling, with a downward
movement to several exhaust inlets located on opposite walls,
is probably the most effective air movement pattern for
maintaining the concentration of contamination at an acceptable
Completely perforated ceilings, partially perforated ceilings,
and ceiling- mounted diffusers have been applied successfully
( Operating room suites are typically in use no more than
8 to 12 h per day (excepting trauma centers and emergency
departments). For energy conservation, the air-conditioning
system should allow a reduction in the air supplied to some
or all of the operating rooms when possible. Positive space
pressure must be maintained at reduced air volumes to ensure
The time required for an inactive room to become usable
again must be considered. Consultation with the hospital
surgical staff will determine the feasibility of this feature.
A separate air exhaust system or special vacuum system should
be provided for the removal of anesthetic trace gases .
Medical vacuum systems have been used for removal of nonflammable
anesthetic gases (NFPA Standard 99).
One or more outlets may be located in each operating room
to permit connection of the anesthetic machine scavenger
hose. Although good results have been reported from air
disinfection of operating rooms by irradiation, this method
is seldom used. The reluctance to use irradiation may be
attributed to the need for special designs for installation,
protective measures for patients and personnel, constant
monitoring of lamp efficiency, and maintenance.
The following conditions are recommended for operating,
catheterization, cystoscopic, and fracture rooms:
1. The temperature set point should be adjustable by surgical
staff over a range of 17 to 27°C.
2. Relative humidity should be kept between 45 and 55%.
3. Air pressure should be maintained positive with respect
to any adjoining rooms by supplying 15% excess air.
4. Differential pressure indicating device should be installed
to permit air pressure readings in the rooms. Thorough sealing
of essential to maintaining readable pressure.
5. Humidity indicator and thermometers should be located
for easy observation. 6. Filter efficiencies should be in
accordance with Table 1.
7. Entire installation should conform to the requirements
of NFPA Standard 99, Health Care Facilities.
8. All air should be supplied at the ceiling and exhausted
or returned from at least two locations near the floor for
minimum ventilating rates). Bottom of exhaust outlets should
be at least 75 mm above the floor. Supply diffusers should
be of the unidirectional type. High-induction ceiling or
sidewall diffusers should be avoided.
9. Acoustical materials should not be used as duct linings
unless 90% efficient minimum terminal filters are installed
of the linings. Internal insulation of terminal units may
be encapsulated with approved materials. Duct-mounted sound
traps should be of the packless type or have polyester film
linings over acoustical fill.
10. Any spray-applied insulation and fireproofing should
be treated with fungi growth inhibitor.
11. Sufficient lengths of watertight, drained stainless
steel duct should be installed downstream of humidification
equipment to assure complete evaporation of water vapor
before air is discharged into the room. Control centers
that monitor and permit adjustment of temperature,
humidity, and air pressure may be located at the surgical
The pressure in the obstetrical department should be positive
or equal to that in other areas.
Delivery Rooms. The design for the delivery room should
conform to the requirements of operating rooms.
Recovery Rooms. Postoperative recovery rooms used in conjunction
with the operating rooms should be maintained at a temperature
of 24°C and a relative humidity between 45 and 55%.
Because the smell of residual anesthesia sometimes creates
odor problems in recovery rooms, ventilation is important,
and a balanced air pressure relative to the air pressure
of adjoining areas should be provided.
Nursery Suites. Air conditioning in nurseries provides
the constant temperature and humidity conditions essential
to care of the newborn in a hospital environment. Air movement
patterns in nurseries should be carefully designed to reduce
the possibility of drafts. All air supplied to nurseries
should enter at or near the ceiling and be removed near
the floor with the bottom of exhaust openings located at
least 75 mm above the floor. Air system filter efficiencies
should conform to Table 1. Finned tube radiation and other
forms of convection heating should not be used in nurseries.
Full-Term Nurseries. A temperature of 24°C and a relative
humidity from 30 to 60% are recommended for full-term nurseries,
examination rooms, and work spaces. The maternity nursing
section should be controlled similarly to protect the infant
during visits with the mother. The nursery should have a
positive air pressure relative to the work space and examination
room, and any rooms located between the nurseries and the
corridor should be similarly pressurized relative to the
corridor. This prevents the infiltration of contaminated
air from outside areas. Special Care Nurseries. These
nurseries require a variable range temperature capability
of 24 to 27°C and a relative humidity from 30 to 60%.
This type of nursery is usually equipped with individual
incubators to regulate temperature and humidity. It is desirable
to maintain these same conditions within the nursery proper
to accommodate both infants removed from the incubators
and those not placed in incubators. The pressurization of
special care nurseries should correspond to that of full-term
Observation Nurseries. Temperature and humidity requirements
for observation nurseries are similar to those for full-term
nurseries. Because infants in these nurseries have unusual
clinical symptoms, the air from this area should not enter
other nurseries. A negative air pressure relative to the
air pressure of the workroom should be maintained in the
nursery. The workroom, usually located between the nursery
and the corridor, should be pressurized relative to the
corridor. Emergency Rooms. Emergency rooms are typically
the most highly contaminated areas in the hospital as a
result of the soiled condition of many arriving patients
and the relatively large number of persons accompanying
them. Temperatures and humidities of offices and waiting
spaces should be within the normal comfort range. Trauma
Rooms. Trauma rooms should be ventilated in accordance with
requirements in Table 3. Emergency operating rooms located
near the emergency department should have the same temperature,
humidity, and ventilation requirements as those of operating
rooms. Anesthesia Storage Rooms. Anesthesia storage rooms
must be ventilated in conformance with NFPA Standard 99.
However, mechanical ventilation only is recommend