Air sanitation is the system of removing the impurities present in air inside buildings to protect people from infections. Sanitation of air is essential in enclosed places like hospitals and operation rooms.

2. Why sanitation of air is essential?
 To prevent infection
 To prevent contamination

3. Methods of air sanitation
• Sanitation of air can be effected in a number of ways each having its own
applications.
Chemical
methods
Mechanical
methods
Ultraviolet
light
Electrostatic
precipitation
Heating
methods

4.  Air sanitation can be done by the use of certain
gaseous chemical agents.
 These agents are mostly used to sterilize air in an
enclosed space.

5. 1) Hypochlorous acid
• Hypochlorous acid or a hypochlorite like sodium hypochlorite.
• Used in a final concentration of 1:2 million.
• This concentration is sufficient to reduce bacteria as well as viruses
like influenza virus.
• Its effectiveness depends upon the moisture content of air.
• Slightly increased relative humidity (RH 90%) rapidly kills
Streptococci and Staphylococci.

6. 2) Quaternary ammonium surface active disinfectant
• Commercially available disinfectant
• Used as an air sanitizing agent.
• Reduce the number of airborne and surface bacteria in hospital
rooms when this compound is spray-fogged.
• Fogging procedures (are effectively used to decontaminate the
rooms vacated by patients infected with staphylococci, streptococci,
pseudomonads and Salmonella.

7. 3) Glycols
• Propylene glycol and triethylene glycol are active against Streptococci,
staphylococci, pneumococci, H. influenzae and influenza virus
• Concentration - 1:4 million.
• Maximum microbicidal activity - at temperature - 27°C and RH - 45-70%.
• The bactericidal activity of glycols are due to their hygroscopicity.
• When glycol molecules are atomized into the air they dissolve in the film of
moisture surrounding each microorganism. At a particular concentration of
glycol, the moisture inside the bacterial cell is drawn out of the cell and this
leads to the death of the microbe.

8. Limitations
• (1) it is difficult to maintain a desired concentration
because of the deposition of the agents on surfaces and
• (2) large volumes of agents are required to maintain the
final concentration.
• (3) No chemical agent has been found to be successful.

9. • Mechanical methods are aimed at the removal/reduction of
microorganisms.
Suppression of dust
Filters
Laminar air flow

10. Suppression of dust
• Dust particles act as a substratum for microorganisms
• Microbes adhere and remain viable for quite long period.
• Bacteria carrying dust particles can either remain suspended in air
or they may settle down on various objects.
• It depends on factors - air current and weight of the particle,
• Dust particles helps in the dispersion of microorganisms in air.

11. • So any procedure that suppresses the emergence or distribution of dust
will in turn affect the microflora of air.
• Applying oil emulsion to floors, bed cloths and other textiles will
provide an effective control over dust and dust borne bacteria.
• Oil mechanically inhibits the spread of dust by binding to them,
• Simple, practicable and economical.
• This method considerably reduce the incidence of respiratory tract
infections.
• Removal of dust using vacuum pump followed by application of
disinfectant solution has also been recommended.

12. Filters
• Filtration is also a method of air sanitation,
• Particles size - larger than 5μm.
• The microbes can be removed by passing the air through simple filters
• High efficiency filters can be used for smaller particles.
• The various types of filter materials used in air sterilization
o 1. Granular - activated charcoal;
o 2. Fibrous pads - cotton wool, slag wool, and glass wool;
o 3. Filter papers - cellulose - asbestos and glass fibre.

13. HEPA Filters
• High efficiency particulate air (HEPA) filters are
specially designed filters to deliver clean, sterile air into an
enclosed room or cabinet.
• The filter material is made up of fiberglass.
• Pore size - 0.3μm
• Efficiency - 99.9%.
• Usually disposable pre-filter (reduces the load) is used
along with the main filter.
• Use of HEPA filter - laboratory safety cabinets where the
incoming air is filtered and the used air is decontaminated
as the air passes through the filter.
• HEPA filters are also used in hospitals to provide sterile air.
• Limitation - costly.

14. Types of HEPA Filters
Classification Types Performance Application
HEPA Filter
Class H
A 99.97% for 0.3 μm particles MMD
(Mass Median Diameter)
Industrial
C 99.99% for 0.3 μm particles MMD Laminar flow
ULPA Filter
Class U
F 99.999% for 0.1 - 0.2 μm particles Ultra-low penetration air (ULPA)
Minimum particle collection
efficiency
G 99.9999% on MPPS (Most
penetrating particle size)
Super ULPA
According to the Institute of Environmental Science and Technology, (IEST)
with regard to performance, there are 6 types – A, B, C, D, E & F. Each has its
own distinct characteristics

15. Laminar air flow
• Its an unidirectional flow of air.
• Air is continuously flowing at high pressure in one
direction.
• Air flow prevents the dissemination of microorganisms
into outside air.
• HEPA filters were used.

17. • Radiation of short wave lengths are more powerful in controlling airborne
microorganisms.
• Among these ultraviolet (UV) is the widely used one.
• UV wavelength range - 210-328 nm.
• Max. microbicidal effect of UV light - around 260nm (absorption
wavelength for DNA).
• Modern low pressure mercury vapour lamps
• emit more than 95% of their radiation at 253.7nm – max. microbicidal
activity.

18. Mechanism
• Various photo products are produced in microbe when
exposed to UV.
 Purine & Pyrimidine dimers b/w the adjacent bases in DNA.
 Induce NA-Ptn crosslinks.
 In Deinococcus radiodurans - 5, 6-dihydroxy dihydrothymine,
 In bacterial spores - 5 thyminyl 5-6 dihydro thymine (TDHT),
• Unless removed, these photo products form non coding lesions in
DNA which ultimately lead to cell death.

19. Factors influencing UV sterilization
Factors
Type of organism
veg. cell/spores
Type of
suspension
dry/wet forms
Cell number
Effect of
Temperature
lowT is sensitive
Effect of organic
matter
req. increased dose of UV
Repair
mechanism

20. • The airborne dust particles containing
microorganisms are subjected to electric field.
• When the air is passed through an ionizer the
dust particles are charged.
• From the ionizer the charged particles are
carried through a collector which contains both
negative and positive electrodes.
• Charged dust particles are deposited on the
electrodes of opposite charge.
• It is an highly efficient process but costly.

21. • Heating can also be used as an air sanitation method.
• Sterile air can be produced by passage through a heated
pipe.
• The temperature of air must exceed 220°C to kill spores and
vegetative forms.
• Limitations - complex and expensive method, very rarely
used.