3. Decontamination
• Decontamination: Any process for removing
and /or killing microorganisms. The same term
is used for removing or neutralizing hazardous
chemicals and radioactive materials
4. Terms used in dealing with
decontamination
• Antimicrobial: An agent that kills microorganism
or suppresses their growth and multiplecation
• Antiseptic: A substance that inhibits the growth
and development of microorganisms without
killing them. Antiseptics are usually applied on
body surface
• Biocide: A general term for any agent that kills
unicellular and multicellular organisms.
• Chemical germicide: A chemical or a mixture of
chemical s used to kill microorganisms.
5. Contd….
• Disinfectant: A chemical or mixture of chemical
used to kill microorganisms , but not necessarily
their spores. Disinfectants are usually applied on
inanimate surface or objects
• Disinfection: A physical or chemical means of
killing microorganisms, but not necessarily their
spores
• Microbicide: A chemical or mixture of chemicals
that kills microorganisms. The term is often used
in place of “Biocide”, “Germicide” or
“antimircobial”
6. Sterilization
• A process that destroys and /or removes all
classes of microorganisms and their spores
7. Precleaning and cleaning laboratory
materials
• Cleaning: Removal of visible dirt and strains
• Chemical germicides: Many types of chemicals
used as disinfectant and antiseptics.
8. Name Clean- Condition Dirty-condition
Available Chlorine (Aq.
NaOCl)
0.1% (1g/L) 0.5% (5g/L)
Sodium hypochlorite
solution (5% available Cl2)
20ml/L 100ml/L
Calcium hypochlorite (70%
available Cl2)
1.4g/l 7.0g/L
Sodium
dichloroisocyanurate
tablets (60 % available Cl2)
1.7g/L 8.5g/L
Chloramine (25% available
Cl2)
20g/L 20g/L
Formaldehyde (formalin),
kills microorganism
&spores
5% liq disinfectant 37% containing methanol
(100ml/L) as stabilizer,
used for enclosed volume
as BSC and rooms .
9. Local environmental decontamination
• For furniture, and equipment
• NaOCl (1g/L) , substitute is 3% hydrogen peroxide
• By fumigation, all opening in rooms must be
closed
• Fumigation conducted at ambient temp, atleast
21 deg C and 70% humidity, 8 hours
• Ammonium bicarbonate can be used to prevent
premature neutralization of HCHO
• HCHO: irritant gas, suspected carcinogenic,
respirators necessary.
10. Decontamination of BSC
• BSC class I,II 0.8% paraformaldehyde should
be placed on an hot electric plate or hot plate
• One hot plate with ammonium bicarbonate
• Humidity-70%
• Sealed or closed with strong duct tape
• Turned on for 1 hour, or when
paraformaldehyde has all vaporized, 1 hour
ammonium bicarbonate
• Left cabinet overnight
11. Hand washing/hand decontamination
• Wash hands (10 sec, throughly)with any soap
with sufficient water, but use of germicidal
soap is recommended for high-risk situations
• Paper towel, and alcohol based hand-rubs
• Use suitable golves
• Hand washing, before & after entering or
leaving the lab
12. Heat disinfectant and sterilization
• Heat is the most common among the physical
agents used for the decontamination (hot-air
oven)
• Dry-heat- totally non-corrosive, used for items
which can stand temp of 160 deg.C for 2-4
hours
• Burning or incineration is also a from of “dry-
heat”
• Moist-heat- is most effective when used as
autoclaving
13. Autoclaving
• Saturated steam under pressure (autoclave) is
the most effective and reliable means of
sterilizing lab materials
• Correctly loaded
3 min holding time at 134 deg C
10 min holding time at 126 deg C
15 min holding time at 121 deg C
25 min holding time at 115 deg C
14. Contd…..
• Gravity displacement autoclaves:
Steam enters the chamber under pressure and
displaces the heavier air downwards and through
the valve in the chamber drain, fitted with a HEPA
filters
• Pre-vacuum autoclaves:
These machines allow the removal of air from the
chamber before steam is admitted. The exhaust air
is evacuated through a valve fitted with HEPA filter.
At the end of the cycle , the steam is automatically
exhausted. Operates at 134Deg C, sterilization cycle
reduced to 3 min, ideal for porous loads, not for
liquids (because of vacuum)
15. Contd…
• Fuel-heated pressure cooker autoclave
• Can be used if gravity displacement is not
available. They are loaded from the top and
heated by gas, electricity or other types of fuel.
Steam is generated by heating water in the base
of the vessel, and air is displaced upwards
through relief vent. When all the air is removed,
the valve on the relief is closed and heat is
reduced. The pressure &temp rise until the safety
valve operates at present level. This is start to the
holding time. At end of the cycle the heat is
turned off and temp is allowed to fall to 80deg C
or below is open the lid.
16. Precautions
1. Materials should be loosely packed, steam
penetration
2. Steam should be free from corrosive inhibitors,
which could contaminate the items being
sterilized
3. Packed in proper plastic bag or containers
4. Trained operator, Routine monitoring, biological
indicators or thermocouples should be placed at
the center of each load is highly desirable
5. Cleaned daily
6. Safety valve checked for any blockage.
17. Incineration
• Useful for disposing animal carcasses as well as
anatomical and other lab waste with or without
prior decontamination
• Incineration, especially those with single chamber
are unsatisfactory and may not completely
destroy the infectious materials
• Ideally , temp of primary chamber should be 800
deg C, and sec. chamber 1000 deg.C
• Environment friendly bags and energy efficient
source should be used.
• Licensed Land fill sites
