Air conditioningAir conditioning
requirements in hospitalsrequirements in hospitals
Microbiological transmission in healthcare
setting is inevitably a very potential risk. The
main routes are droplets, contact, common
vehicle and air borne transmissions. Infection
control for patients, healthcare providers and
visitors is of paramount importance in the
healthcare process in medical facilities. Proper air
conditioning of medical care facilities is helpful
in prevention and treatment of diseases.
Continual advances in medicine and technology
have led to the development in medical care
processes as many new complex diagnostic and
therapeutic procedures have been added to the
armamentarium of medical care.
There is a need for constant evaluation of air
conditioning needs of the hospitals and medical
facilities for better patient care.
What is air conditioning?
Air conditioning (often referred to as aircon, AC or
A/C) is the process of altering the properties of air
(primarily temperature and humidity) to more favorable
More generally, air conditioning can refer to any form of
technological cooling, heating, ventilation, or disinfection
that modifies the condition of air.
Air conditioning is defined as a processAir conditioning is defined as a process
which cools(or heats), cleans, freshenswhich cools(or heats), cleans, freshens
air and controls its moisture contentair and controls its moisture content
Types of air conditioning in hospital
HVAC designer will recommend different types of air
conditioning systems for different applications. most
commonly using are:
1)Window air conditioner: is the most commonly used air
conditioner for single rooms. In this air conditioner all the
components, namely the compressor, condenser,
expansion valve or coil, evaporator and cooling coil are
enclosed in a single box. This unit is fitted in a opening
made in the wall of the room, or more commonly a
2) Split Air Conditioner:
The split air conditioner comprises of two parts: the
outdoor unit and the indoor unit. The outdoor unit, fitted
outside the room, houses components like the
compressor, condenser and expansion valve. The indoor
unit comprises the evaporator or cooling coil and the
cooling fan. For this unit you don’t have to make any slot
in the wall of the room. Further, present day split units
have aesthetic appeal and do not take up as much space as
a window unit. A split air conditioner can be used to cool
one or two rooms.
3) Packaged Air Conditioner
An HVAC designer will suggest this type of air
conditioner which is used to cool more than two rooms or
a larger space at home or office.
There are two possible arrangements with the package
unit. In the first one, all the components, namely the
compressor, condenser (which can be air cooled or water
cooled), expansion valve and evaporator are housed in a
The cooled air is thrown by the high capacity blower, and
it flows through the ducts laid through various rooms. In
the second arrangement, the compressor and condenser
are housed in one casing. The compressed gas passes
through individual units, comprised of the expansion
valve and cooling coil, located in various rooms.
4) Central Air Conditioning System
Central air conditioning is used for cooling big buildings,
houses, offices, entire hotels, gyms, movie theaters,
If the whole building is to be air conditioned, HVAC
engineers find that putting individual units in each of the
rooms is very expensive making this a better option.
A central air conditioning system is comprised of a huge
compressor that has the capacity to produce hundreds of
tons of air conditioning.
Cooling big halls, malls, huge spaces, galleries etc is
usually only feasible with central conditioning units.
Chilled Water Applied Systems
A chilled-water applied system uses chilled water to
transport heat energy between the airside, chillers and the
These systems are more commonly found in large HVAC
installations, given their efficiency advantages.
The components of the chiller (evaporator, compressor,
an air- or water-cooled condenser, and expansion device)
are often manufactured, assembled, and tested as a
complete package within the factory.
High-efficiency particulate air or HEPA is a type of air
The filter must satisfy certain standards of efficiency such
as those set by the United States Department of Energy
To qualify as HEPA by US government standards, an air
filter must remove (from the air that passes through)
99.97% of particles that have a size of 0.3 micro metres
HEPA filters are critical in the prevention of the spread of
airborne bacterial and viral organisms and, therefore,
Typically, medical-use HEPA filtration systems also
incorporate high-energy ultra-violet light units to kill off
the live bacteria and viruses trapped by the filter media.
Some of the best-rated HEPA units have an efficiency
rating of 99.95%, which assures a very high level of
protection against airborne disease transmission.
Why do hospitals really require air
Installing these units in hospitals provides a comfortable
environment to patients. Doctors and staff will also be able
to work more comfortably and concentrate on their duty in a
These days most modern hospitals are equipped with this
air conditioning. The technology is also utilized to provide
various therapies to patients.
According to studies it has been proved that patients show
speedy recovery in controlled environment than in an
uncontrolled environment. For example, cardiac patients
may not be able to maintain adequate circulation to
facilitate standard heat loss. This is also a reason that
cardiac wards and rooms are equipped with air conditioning
Patients within head injuries, those subjected with brain
operations and those with poisoning may have high fever
in a hot environment due to trouble in the brain’s heat
regulatory system. The best thing to ensure recovery here
is to maintain cool and comfortable environment.
Burn patients also require a warm environment with high
relative humidity. The room for severe burn patients must
possess temperature controls that can keep the level of
temperature should be 32 degree Celsius.
The relative humidity should go up to 95 per cent, this is
where air conditioning is used as a clean room
Air conditioning is extremely important in the operation
theater. This helps in controlling the temperature,
humidity and sterile filtration.
These units are also considered as a necessity for other
departments of hospitals such as delivery room,
radiology, recovery room, intensive care unit, CT, &
Air conditioning has helped in making the environment
of hospitals livable and extremely comfortable.
This also facilitates in keeping the environment of the
hospital clean and hygienic. The patients will feel happy,
healthy and comfortable with an air conditioning installed
Need for air conditioning of hospital
Proper air conditioning is helpful in the prevention and
treatment of diseases. The factors determining the need for
air conditioning in hospital facilities are:
(a) The need to restrict air movement within and between
(b) The specific requirements for ventilation and filtration to
dilute and remove contaminants in the form of airborne
microorganisms, viruses, odour, hazardous chemicals and
(c) Different types of temperature and humidity requirements
for various areas.
(d) Permit accurate control of environmental conditions.
(e) Control of air quality and air movement
Infection Sources and Control
Bacterial Infection. Infectious bacteria are transported by
air. Droplet or infectious agents of 5 mm or less in size
can remain airborne indefinitely. It has been shown that
90 to 95 per cent effective filters remove 99.9 per cent of
all bacteria present in hospitals.
Epidemiological evidence and other studies indicate that
many of the air borne viruses that transmit infections are
sub- micron in size, thus there is no known method to
effectively eliminate 100 per cent of the viable particles.
HEPA filters and/or Ultra-Low Penetration (ULPA)
filters provide the greatest efficiency currently available.
Therefore, the isolation rooms with appropriate
ventilation pressure relationships are the primary means
used to prevent the spread of airborne viruses in the
Outdoor air in comparison to room air is virtually free of
bacteria and viruses.
Infection control problems frequently involve a bacterial
or viral source within the hospital. Ventilation air dilutes
the viral and bacterial contamination within the hospital.
Properly designed, constructed and maintained
ventilation systems preserve the correct pressure
relationship between functional areas; they remove
airborne infectious agents from hospital environment.
Indoor Air Quality in Hospitals
Indoor air quality in
hospital is a complex multi-
faceted issue. Contaminants
come with dust, air and
visitors as well as originate
inside the hospital complex
and threaten the quality of
common contaminants are
microbes and organic
Ventilation and filtration
provides a means of
fighting contaminants by
diluting their concentration.
Acceptable indoor air quality can be achieved by
following the fundamental principles:
(a) Contaminant source control.
(b) Proper ventilation.
(c) Humidity management.
(d) Adequate filtration.
The temperature and humidity conditions in hospital
environment can inhibit or promote the growth of
bacteria and activate or deactivate viruses. Ventilation
systems are used to provide air virtually free of dust, dirt,
odour, chemicals and radioactive pollutants.
Contamination can be dispersed into the air of the
hospital environment by one of the many routine
activities of normal patient care.
Because of the dispersal of bacteria resulting from such
necessary activities, air-handling system should provide
air movement patterns to minimize the spread of
The sense of thermal comfort results from an interaction
between temperature, relative humidity, air movement,
clothing, activity levels and individual physiology.
The temperature and relative humidity measurements are
indicators of thermal comfort. The medical care needs of
patients require thermal comfort provided by air
Operating Room Air Conditioning
The primary task of the
ventilation system in an
operating room is to
provide an acceptable
indoor climate for
personnel and patients, to
remove odor, released
anesthetic gases and to
reduce the risk of infection
in the operating area. The
greatest amount of bacteria
found in operating rooms
comes from the surgical
team and is a result of their
activity 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 contaminants in
this highly sensitive area.
Studies of operating room air distribution systems and
various air delivery systems indicate that these are the
most effective methods for air movement pattern in
operation theatres for limiting the concentration of
contaminants to an acceptable level.
The total heat production per hour caused by the staff,
operation room lighting and equipment may be about 2
KW or 1750 Kcal/h.
Operating Room Ventilation
To maintain oxygenation for 10 persons in the operating
room, a volume of about 28 m3 of air will be required per
hour. How much outside air is required for the dilution of
odour will depend on the nature and intensity of odor
It is indicated by some studies that air supplied at 0.24
m3 per minute per person is the critical level of odour
A ventilation rate of 10 air changes per hour reduces the
level of any contamination present in the air by about 99
15 to 20 air changes per hour should be sufficient for
comfort, to ensure pressurization in the operation room
and to maintain considerable control of airborne micro
organisms in an operation room of the size of about 40 sq
meter, if an average surgical team is involved.
Another study shows that bacteriological contamination
of the air is markedly reduced by the use of ultra clean air
Airborne contamination in operating room is mainly
derived from the personnel in the operation theatre and
The number of
ventilation and airflow
implements the bacterial
count in operation
Proper design and
ventilation of operation
theatre is the most
important means of
infection in operation
Empty Operation Theatre
The empty operation theatre should have:
a) Less than 35 colony-forming units (CFU) of bacteria/m3
b) Less than one CFU of Clostridium perfingens or
Staphylococcus aureus in 30 m3.
c) During operation less than 180 CFU/ m3 of air using ultra
clean laminar flow in the theatre.
d) Less than 20 CFU/ m 3 at the periphery of the enclosure
and less than 10 CFU/ m3 at the centre.
Direction of Air Flow
Direction of airflow should be from clean to less clean
Airflow rate of 0.28 -0.47 m /sec is desirable across an
open door to prevent back flow into cleaner area.
In Ultra clean air enclosure, the airflow should not be less
than 0.2 m/sec .
One of the aspects of humidity is that bacteriological
microorganisms ride on dust particles whose attract
ability to one another is favored by low relative humidity
resulting in increased static energy.
Low relative humidity is reported to be suitable for
Klebsiella pneumoniae activity.
High humidity in the hospital enhances the danger of
growth of Pseudomonas aeruginosa.
Humidity in operation room is believed to contribute to
the prevention of dehydration of exposed tissue.
To minimize the explosion risk , the relative humidity
required is 40-65 per cent.
Air conditioning other zones
1) Patient rooms: air conditioning of bed rooms in our warm
humid climate desirable not only for medical reason but
also to keep out noise , pollution from mainly cars &
It is more important in dry areas where dust storm
common in the summer months.
When central air-conditioning system used for pt rooms
avoid ducted air supply and return to the rooms in order
to eliminate chance of cross infection. and to odours
through the common ducts for the same reason, packaged
air conditioner feeding a group of rooms through a ducted
supply must also be avoided.
Use of individual fan coil units in each room
connected to a central chilled water plant and room
thermo stats for indipendent temp control is ideal
2) ICU :These units serves seriously ill pts from post
operative to coronary pts.
There needs of clean filtered air without the possibility
of contamination from adjoining areas and variable
range of temp capability from 24 to 27 °c are important .
3) LABOUR & DELIVERY : The procedures for
normal child birth are considered non invasive and
rooms are controlled similar to pts rooms .
Invasive procedures such as a caesarian section are
performed in an OT .
4)MRI &CT SCAN ROOMS :
Normal comforts AC and
ventilation is required. How
ever the special needs of the
must be checked out and at
times a precision AC may
be called for to handle the
high heat release of
computer equipment and
cryogens used to cool the
5) AUTOPSY ROOM :
comforts conditions are
maintained with a 100%
fresh air system with full
exhaust . Due to heavy
and odor, autopsy room
require special attention
for exhausting all air above
the roof of the hospital . To
prevent spread of
contamination to adjoining
areas ,the autopsy room
must be maintained at –ve
THERAPHY DEPT :
The normal AC cooling
load of the electro
therapy section is
affected by the short
wave diathermy ,
infrared and ultraviolet
equipment used in this
The exercise section
requires no special
treatment and temp and
humidity should be
within the comfort zone.
7)CSSD : comfort Ac is optional but ventilation and exhaust
air system are essential . Used and contaminated utensils,
instruments and equipment are brought to this unit for
cleaning and sterilization prior to reuse. the dept usually
consists of cleaning area ,a sterilizing area and a storage
area where supplies are kept until requested. the storage
area should preferably be air conditioned on 24 hour basis
in case the remaining CSSD dept in merely ventilated.
8) KITCHEN: This is generally
ventilated, meaning that fresh
filtered air is distributed to the
entire area and stale air exhausted
through the hoods kept over the
cooking area where the heat is
cooler and freezer rooms are
located close to the kitchen area
and the refrigeration equipment
and for these should preferably be
water cooled for the best cooling
the dietitian’s office is often
located within or adjoining the
kitchen . It is usually completely
enclosed to ensure privacy and
noise reduction and air
conditioned for comfort.
9) LAUNDRY: this is
another area which is
generally ventilated with
fresh filtered air and
exhausted through hoods
placed over the heat
equipment such as
washers ,flat work
ironers and tumblers .
special advice must be
taken from the
and all exhaust should
terminate above the roof
or where it’ll not be are
nuisance to neighbors
10) PHARMACIES AND DRUG STORAGE AREAS:
Are another unit within hospitals and other healthcare
organizations than require air conditioning in order to
carry 'temperature dependent' drugs.
Inadequate temperature control here either means that
medication would not function as required or the hospital
would simply not be able to stock some emergency
Disadvantages of air conditioners
Air conditioners use a lot of electricity.
spending too much time in an air-conditioned
environment can contribute to health problems such as
asthma, tightness in the chest and other respiratory
Low temperatures will lead to a sharp contraction of
blood vessels, poor blood flow and joint pain.
the temperature difference between indoor and outdoor,
people often will feel hot and cold, this will result in the
body conditioning system disorders.
The benefit to the clientele, prompt recovery, restoration
of quality of life, disability limitation, prevention of
hospital acquired infection, enhancing the productivity of
the equipment and staff cannot be quantified in to the
exact financial terms. A single case of hospital acquired
infection requires at least double the duration of stay in
hospital, which leads the antibiotic cost to manifold, leads
to increase in the cost due to management of antecedent
complications and loss of productive man-hours, justifies
the case for air conditioning. The hospitals/medical
institution deals with life of the clientele, the lives saved
by providing appropriate therapeutic, diagnostic and
treatment facilities justify that the investment for air
conditioning is a small cost for better quality care to the