how to choose a suitable bsc for your lab for becthai

How to Select a Suitable Biosafety

Cabinet for Your Laboratory

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วิมลา

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By Wimala Horwongsakul

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6

How Biosafety Level is Defined?

7

Infective Microorganisms by Risk Group

Source: WHO Laboratory Biosafety Manual. 3rd Edition. 2004

Definition Examples

Risk Group 1 (no or low individual and community risk) A microorganism that is unlikely to cause human or animal disease

E. coli K12,

Asporogenic Bacillus subtilis

Baculoviruses, Herpesvirus saimiri

Risk Group 2 (moderate individual risk, low 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 preventive measures are available and the risk of

spread of infection is limited

E. coli, Neisseria meningitidis

Treponema pallidum

Cryptococcus neoformans

Ascaris spp., Leishmania spp.

Adenovirus.

Hepatitis A – E

Risk 3 (high 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 and

preventive measures are available

Brucella spp.

Coxsiella burnetti

Mycobacterium tuberculosis

Coccidioides immitis

Alphaviruses (VEE)

Hantaviruses, Monkeypox

Risk 4 (high individual and 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.

Lassa virus

Machupo virus

Ebola virus

Marburg virus

Herpesvirus simiae

Hemorrhagic fever viruses

8

Relation of Risk Groups to Biosafety Levels


9

Safety – Biosafety

Biosafety

Level 1

(BSL1)

. . .work is done with defined and

characterized strains of viable

microorganisms not known to consistently

cause disease in healthy adult humans.

. . . standard microbiological practices with

no special primary or secondary barriers

recommended, other than a sink for

handwashing.

Biosafety

Level 2

(BSL2)

. . . work is done with the broad spectrum

of indigenous moderate-risk agents that

are present in the community and

associated with human disease of varying

severity.

. . . procedures with aerosol or high splash

potential that may increase the risk of such

personnel exposure must be conducted in

primary containment equipment, or in

devices such as a BIOLOGICAL SAFETY

CABINET or safety centrifuge cups.

Biosafety

Level 3

(BSL3)

. . .work is done with indigenous or exotic

agents with a potential for respiratory

transmission, and which may cause

serious and potentially lethal infection.

All laboratory manipulations should be

performed in a BIOLOGICAL SAFETY

CABINET or other enclosed equipment,

such as a gas-tight aerosol generation

chamber.

Biosafety

Level 4

(BSL4)

. . . work with dangerous and exotic agents

that pose a high individual risk of life-

threatening disease, which may be

transmitted via the aerosol route and for

which there is no available vaccine or

therapy.

All manipulations of infectious materials

within the facility must be conducted in the

Class III biological safety cabinet

OR All procedures must be conducted by

personnel wearing a one-piece positive

pressure suit ventilated with a life support

system.

Source: NSF International Standard for Biosafety Cabinetry, 2004

10

Summary of Biosafety Level Requirements


11

A Typical Biosafety Level 1 Laboratory

Risk Group 1

Biosafety Level Basic – Biosafety

Level 1

Laboratory Type Basic Teaching,

Research

Laboratory Practices GMT

Safety Equipment None; open bench

work

GMT = good microbiological techniques

12


Risk Group 2


Level 2

Laboratory Type Primary health

services; diagnostic

services, research

Laboratory Practices GMT plus protective

clothing, biohazard

signs

Safety Equipment Open bench plus

BSC for aerosols

Procedures likely to generate aerosols are performed within a biological safety cabinet. Doors are kept closed

and are posted with appropriate hazard signs. Potentially contaminated wastes are separated from the general

waste stream

13


Risk Group 3


Level 3

Laboratory Type Special diagnostic

services, research

Laboratory Practices Level 2 + special

clothing, access

control, directed

airflow

Safety Equipment BSC and / or

primary devices for

all activities

The laboratory is accessed through an anteroom (double door entry or basic laboratory – Biosafety Level

2) or an airlock. An autoclave is available within the facility for decontamination of wastes prior to disposal.

A sink with hands-free operation is available. Inward directional airflow is established and all work with

infectious materials is conducted within a biological safety cabinet.

14

Classification of BSC How should we Select BSC?

15

Types of BSC

16

Differences between Class I, II and III BSCs

17

Class I BSC

• For personnel and environmental protection

but not for product protection, having an

open front, with negative-pressure inward

airflow for personnel protection, and

HEPA filtered exhaust air for

environmental protection.

• Use to enclose equipment (e.g. centrifuges,

small fermenter) or for procedure which may

generate aerosols (e.g. tissue

homogenization)

• Does not have to be ducted, but the vast

majority are ducted. Can be used in

BSL3 labs

0.38 m/s

18

Class III BSC

• A totally enclosed, ventilated cabinet of leak-tight

construction. Operations in the cabinet are

conducted through tightly attached gloves. The

cabinet is maintained under negative air pressure

of at least 120 Pa below that of the experiment.

Downflow air is drawn into the cabinet through

HEPA filters. The

exhaust air is treated by

double HEPA filtration or

by HEPA filtration and

subsequent incineration.

19

Class II BSC

• For personnel, product and environmental

protection, having an open front, via which

the operator can operate in the cabinet, with

negative-pressure inward airflow for

personnel protection, downward HEPA

filtered airflow for product protection and

HEPA filtered exhausted air for

environmental protection.

• Can be used with infectious agents in Risk

Group 2 & 3.

• Can be used with Risk Group 4 agents when

positive-pressure suits are used

20

The Types of Class II BSC

Comparison

of Types

Four Key Elements

BSC Exhaust Minimum

Inflow

Exposed Positive

Pressure Contaminated

Plenums

Recirculation

Class II, Type A1

BSC

To Room or through

canopy

0.4

m/s Allowed Mixed

Class II, Type A2

BSC

To Room or through

canopy

0.5

m/s Not allowed Mixed

Class II, Type B1

BSC Direct Connection

0.5

m/s Not allowed Partial

Class II, Type B2

BSC Direct Connection

0.5

m/s Not allowed None

21

Types of Class II BSC

• Contaminated plenum

under +ve pressure

• Min. intake 0.38m/s

• Not for volatile toxic

chemicals

30%

70%

0.51m/s 0.38m/s

0.51m/s

0.51m/s

• Contaminated ducts

and plenum under -ve

pressure


• Can be for minute

quantity of volatile

hazardous material if

properly exhausted



pressure


• Can be for minute

quantity of volatile

hazardous material

Total

Exhaust



pressure


• Reserved for works

where volatile material

recirculation must be

avoided

22

Class II Type A2 BSC

0.5 m/s

• Must be externally exhausted

• Minimum inflow of 0.5 m/s

• No positively pressurized contaminated plenums

• Mixed recirculation

23

Class II Type B2 BSC

0.5 m/s

• Must be externally exhausted

• Minimum inflow of 100 fpm / 0.51 m/s

• No positively pressurized contaminated plenums

• No recirculation / Total Exhaust

• No partial recirculation

• No mixed recirculation

24

B2 Better than A2?

1220 m3/h

740 m3/h

480 m3/h 494 m3/h

494 m3/h

808 m3/h

• B2 are designed for applications involving volatile toxic chemicals or radio-

nuclides (in addition to microbiological work)

• B2 do not provide a higher degree of biological protection

• B2 requires direct duct with dedicated fans.

• A2 can be configured as re-circulating. They can also be Ducted and used as

Thimbles if there are traces of chemicals present

• B2 is exhausting nearly 2 ½ times more air directly out of the Laboratory

B2

100% Externally

Exhausted

A2

30% Exhausted

Extra Cost

• External Motor / Fan

• Ductwork / Damper

• Volume of air exhausted

• Electricity consumption

28

Selection of BSC by Risk Group


Type of Protection BSC Selection

• Personnel protection, microorganisms

in Risk Group 1-3 Class I, Class II, Class III


in Risk Group 4, glove-box laboratory Class III


in Risk Group 4 suit laboratory Class I, Class II

• Product Protection Class II, Class III only if laminar

flow included

• Volatile radionuclide / chemical

protection, minute amounts

Class II B1, Class II A2 vented to

the outside

• Volatile radionuclide / chemical

protection Class I, Class II B2, Class III

29

Selection of BSC by Risk Assessment

Source:

CDC and NIH: Primary Containment of Biohazards: Selection, Installation and Use of BSC. 2nd Edition. 2000

46

We Should Care for Inflow Air

• Locations [1], [2], [3] are not suitable because they are

exposed to drafts from windows and doors

• Location [5] is undesirable because it is in range of plant

traffic and within the exhaust air range of a ventilation

system [4]

• Preferred locations [6], [7], [8] because they are in a draft-

free section of the room and not exposed to plant traffic

• Air barrier at the front opening is

susceptible to air movement • Located out of traffic patterns and away

from room air currents.

• Other devices that might move air • Room supply air vent

• Ventilation fans from electronic devices

• Swinging room doors

• Doors from refrigerators, autoclaves,

and incubators

• Standard room fans or window-mounted

air conditioners

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