2 - BIOSAFETY CABINET Flashcards
are enclosed workspaces with a
ventilated hood that is designed to contain pathogenic microorganisms
during microbiological processes.
Biological Safety Cabinet
is an engineering control intended to protect laboratory workers, the laboratory environment, and work materials from exposure to infectious or biohazardous aerosols and splashes.
Biological Safety Cabinet
What does BSC uses to provide protection
uses inward directional airflow,
high-efficiency particulate air (HEPA) filtration,
laminar airflow
Air is guided in only one direction, towards the inside of the BSC and away from you. Contaminated air is kept inside the BSC. This is called
inward directional flow
HEPA-filtered air flows downward onto the work surface. The airflow is parallel, smooth, and does not easily mix while you work.
Laminar airflow
Air exhausted from the BSC is HEPA-filtered and may be either
recirculated or removed
❑It removes the most penetrating particle size (MPPS) of 0.3 μm with an efficiency
of at least 99.97 %
HEPA (High efficiency particulate air) Filter
The typical HEPA filter is a
single sheet of borosilicate fibers treated with a wet-strength water-repellant binder
HEPA removes particulate matter by this three mechanisms
interception, impaction, diffusion
The HEPA filtering efficiency depends upon
fiber diameter, filter thickness and face velocity
The filter medium is pleated to increase the overall surface area, with pleats being separated by
corrugated aluminum tubes
(HEPA Filtration Mechanisms)
- larger particles are unable to avoid fibers by following the curving contours of
the air stream and are forced to embed in one of them directly
Impaction
(HEPA Filtration Mechanisms)
- particles below 0.3 μm are captured by this mechanism in a HEPA filter. As a result of the collision with gas molecules by the smallest particles, especially those below 0.1 μm in diameter. The small particles are effectively blown or bounced around and collide with the filter media fibers.
Diffusion
(HEPA Filtration Mechanisms)
- particles following a line of flow in the air stream come within one radius of a fiber and adhere to it. Mid size particles are being captured by this process.
Interception
A microorganism that is unlikely to cause human disease or animal disease.
❑Risk Group 1 (no or low individual and community risk)
- A pathogen that can cause human or animal disease but is unlikely to be a serious hazard to laboratory workers, the community, livestock or the environment. Laboratory exposures may cause serious infection, but effective treatment and preventative measures are available and the risk of spread of infection is limited.
❑Risk Group 2 (moderate individual risk, low community risk)
A pathogen that usually causes serious human or animal disease but does not ordinarily spread from one infected individual to another. Effective treatment and
preventive measures are available.
❑Risk Group 3 (high individual risk, low community risk)
A pathogen that usually causes serious human or animal disease and that can be readily transmitted from one individual to another, directly or indirectly. Effective treatment and preventive measures are not usually available.
❑Risk Group 4 (high individual and community risk)
is the most basic biosafety cabinet that provides protection to the environment and the laboratory personnel.
Class I
are typically used to either enclose specific equipment like centrifuges or
for procedures like aerating cultures that might potentially generate aerosols.
Class I
Biosafety cabinets of this class are either ducted (connected to the building exhaust system) or unducted (recirculating filtered exhaust back into the laboratory).
Class I
❑The room air is drawn in through the opening that also allows the entry of the operator’s arm during work.
❑The air inside the cabinet then takes in the aerosol particles that may have been generated and moves it away from the operator towards the HEPA filter.
❑The air moving out of the cabinet is thus, sterilized via the HEPA filters before its discharge to the environment.
Class I
is a ventilated cabinet, which provides personnel, product, and environmental protection
Class II
provide both kinds of protection since makeup air is also HEPA-filtered.
Class II
❑The principle of operation of Class II cabinets involves a fan mounted in the top of the cabinet that draws a curtain of sterile air over the workstation where the biological products are being handled.
❑The air then moves underneath the work station and back up to the top of the cabinet before passing through the HEPA filters.
Class II
❑The exhaust that moves out of the facility consists of air being drawn into the front of the cabinet underneath the work surface.
❑The air drawn in acts as a barrier against the potentially contaminated air coming back out to the operator.
Class II
The alarm on/off switch. The alarm will sound when the sash is raised above the height designated on the BSC.
Alarm Switch
The on/off switch for the blower motor. The blower motor controls airflow in the BSC
Cabinet blower switch
A connection to the building exhaust system on top of a BSC which includes one or
more openings or gaps. An audible and a visual alarm will notify the user of a potential loss in canopy containment.
Canopy (also called a thimble) and alarm
The connection to the building exhaust system on top of a BSC that is air tight with no openings or gaps. Also called “hard duct.”
Direct duct
The large pan below the BSC work surface that retains spillage from the work area. Commonly referred to as a catch basin.
Drain spillage trough
The lever that opens and closes the drain for liquid under the work surface from the drain spillage trough.
Drain valve
The air vent in the work surface at the front opening of a BSC.
Front grille
: A filter with a minimum biological particulate removal efficiency of 99.97%.
HEPA Filter
The on/off switches for the fluorescent light and ultraviolet light in a BSC.
Light Switch
The on/off switch for the power outlet inside a BSC.
Power outlet switch
The gauge that reads in units and referred to as “inches of water.” It is an indication of the
static pressure inside of a cabinet plenum.
Pressure differential gauge/magnehelic gauge
The air vent in the work surface at the back wall of the BSC
Rear grille
The front sliding window of a BSC
Sash
The on/off valve located on the side of a BSC and used to connect to the building vacuum system.
Vacuum petcock
The work area inside a BSC.
Work surface
▪Internal fan – draws room air – 75lfm (linear feet/min) velocity
▪Supply air flows through HEPA – particulate free air to the work surface
Class II A1
▪Reduced turbulence
▪Reduced cross contamination
▪Downward moving air – splits into two: 1) To the front grille 2) To the rear grille
Class II A1
▪30% of the air – exhaust HEPA filter
▪70% of the air – recirculates through HEPA filter back into the work zone of the cabinet
Class II A1
▪Not to be used for work involving volatile toxic chemicals
▪Exhaust the air outside the building ( through use of canopy hood and filter housing )
Class II A1
▪ Inflow air velocity 100lfm
▪all positive pressure contaminated plenums within the cabinet are surrounded by a
negative air pressure plenum —-> ensures leakage
Class II A2
▪Approximately 60% to 70% of the contaminated air is recycled and pushed back into the workstation in the chamber through the downflow HEPA filter, while the remaining 30% to 40% is exhausted through the exhaust HEPA filter
Class II A2
❑ For hazardous chemicals and carcinogens
❑Inflow velocity 100lfm
Class II B1
❑uses single-pass airflow to control the flow of hazardous vapors
❑divides the airflow so that the contaminated air is directed towards the exhaust system while the air between the operator and the workstation mixes with the inflow and is recirculated.
Class II B1
❑The exhaust air dispersed out of the facility should be passed through the HEPA filters to
provide protection to the environment.
❑These cabinets have a dedicated duct system which allows the release of the contaminated
air out of the facility.
❑40% of the air —-> recirculated, 60% —> exhausted out of the facility.
Class II B1
▪Total exhaust cabinet
▪No air recirculation
▪Simultaneous biological and chemical containment
Class II B2
▪Inflow air velocity 100lfm
▪Exhaust 1200 cubic feet/min of room air
Expensive cabinet –> high cost of heavier gauge and higher capacity exhaust fan
hence only for research
Class II B2
located near the work surface, supplies
HEPA-filtered air downward to the work surface.
supply HEPA Filter
located near the top of the BSC,
exhausts HEPA-filtered air back into the laboratory or to the outdoors through a canopy connection to the building exhaust system.
exhaust HEPA Filter
is a dedicated BSC exhaust connection that incorporates one or more small
openings or air gaps between the top of the BSC and the building exhaust system.
Canopy
allows a BSC to exhaust noxious or toxic vapors directly from the cabinet to the
outdoors. Not all Type A2 BSCs will have this.
Canopy
have no within-cabinet recirculation; 100% of the exhaust is HEPA-filtered and exhausted to the outdoors.
Type B2 BSC
recirculate some HEPA-filtered air into the BSC but exhausts the majority of the HEPA-filtered air to the outdoors.
Type B1 BSC
Uses to work with volatile chemicals and radionuclides
Type 1 and Type 2 BSC
- are leak-tight, totally enclosed but ventilated cabinets, where all air that either enters or leaves through the facility pass through a HEPA filter.
❑The cabinets are provided with rubber gloves that are attached to the system to be used
during operations in the cabinet.
Class III
❑The cabinet even has a transfer chamber that facilitates the sterilization of materials before they leave the glove box.
❑Even though the gloves restrict the hand movement of the operator inside the cabinet, it prevents direct contact between the operator and the samples.
Class III
In Class III, the exhaust air is treated with
double HEPA filters
❑Highly infectious agents, hazardous operations
❑Non opening view window
❑Passage of materials through a dunk tank
Class III
❑Double door pass through box with autoclave
❑ Supply and exhaust air –> HEPA
❑Negative pressure cabinet
❑Long heavy duty rubber gloves attached in a gas tight manner to port in the cabinets
Class III
