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Biosafety laboratories and environmental management of biological risk

The World Health Organization (WHO) has recognized long ago the importance of safety and biosafety by providing the international guidelines on safety and security.
Among the topics discussed there is the planning of laboratories which will be divided in: basic (level 1 and 2), containment (level 3 or BLS3) and maximum containment (level 4 or BLS4). The level of biosafety needed for each laboratory is related to the structural characteristics of the laboratory, its containment capacities, equipment, activities and the necessary procedures to work with the biological agents belonging to the four categories. The level is assigned after evaluating the risk involved and it must be based not only on the group risk of the pathogen agent. For example if I was working with a pathogen agent group with highly concentrated aerosols I would need a biosafety level three because it ensures a better containment.
In order to plan these laboratories it is necessary to take into consideration not only the structures but also the equipment which is chosen according to the duration of the activity with a set biological agent.
In the following chart, taken from the WHO manual there is a summary of what has been above mentioned:

Risk groups for biosafety levels

Groups  Biosafety level Type of laboratory Practices   Equipment
1 Base Level 1 Basic training and research

Good laboratory practice

None, work station  
2 Base Level 2 Basic diagnostics, research

Good laboratory practice, individual protection tools and warning sign

Working station plus biosefety cabinet for the procedures which produce aerosol

3 Containment level 3 Specialised diagnostics, research

As in level 2 plus special IPD, controlled access, ventilation without recirculating ventilation

Safety cabinets for all procedures
4 Maximum containment level 4 Dangerous pathogens

As in level 3 plus authorized entrance, decontamination shower and a proper disposal system for single-use materials

Class II biosafety cabinets (glove box) or pressurized suits with class II cabinets and a pass-through autoclave and a ventilation system through high efficiency filters


This article will deal with the structural measures of containment for the BS3 and BS4 laboratories which are the most important as shown in the following chart:

Containment levels characteristics

                                                                  Biosafity level
  1 2 3 4
The working area must be separated from any other activity taki ng place in the same buildinga  No No Yes Yes
The working area must be sealed tight in order to allow the sanitisation of the place No No Yes Yes
  • the working area must be kept under a negative pressure with respect to atmospheric pressure
No Preferred Yes Yes
  • controlled ventilation system
No Preferred Yes Yes
  • the extracted air in the working area must be filtered through an HEPA filter
No No Yes/Nob Yes
Double door access No No Yes Yes
Filter area with interlocked sealed tight doors No No  No Yes
Filter area with interlocked sealed tight doors and an airshower No No  No Yes
Filter room No No Yes -
Filter room with an airshower No No  Yes/Noc  No
Decontamination treatment of discharges No  No  Yes/Noc  Yes
  • nearby
No Preferred  Yes Yes
  • in the laboratory
No  No  Preferred Yes
  • pass-through
No  No  Perferred Yes
Biosafety cabinets No Preferred  Yes  Yes
The possibility to see the staff from the outsided No No  Preferred  Yes


a Environmental and functional to the genral traffic
b According to where the air handler is placed (see chapter 4)
c According to the biological agents used in the laboratory
d Example, inspection window, internal tv circuit, double way access

Aside from the basic equipment the BSL3 and BSL4 must be separated from passage areas through a filter zone with automatically closing and interlocked doors so that they open one at a time. The whole laboratory must be easy to decontaminate and all surfaces must be easily washable. The laboratory must be sealable in order to carry out a decontamination process by gas.
In order to avoid the aerial dispersion of microorganisms, ventilation must have a negative pressure. The air in the laboratory can be filtered using HEPA filters high efficiency particu-late air. This is a high efficiency filtration system which uses reconditioned air and makes it flow in the laboratory. The air that comes out of the laboratory (with the exception of the air the comes out of the biological safety cabinet) must be directly released outside of the building in order to be far away from the other buildings and air intake devices. The air release systems must have HEPA filters depending upon the agents which are being used.
The water supply must be equipped with systems that prevent rip currents and there must be a sink with a tap that can be used without using your hands and next to each exit.

Aside from these structural characteristics, a level 4 maximum containment laboratory needs:

  • Primary containment: this can be made by using CLASS III laminar flow cabinets which must be placed in in a separate designated place accessible through a minimum of two doors. There must be a number of filter areas and they must be different from the one which is shower equipped. Finally to introduce any kind of material inside it is necessary to install a fumigation chamber or an Interlocking double-door autoclave. Alternatively the containment is feasible through the usage of pressurized overalls, but since they are not a planning measure they will not be treated in this article.
  • Decontamination of discharges: all discharges coming from the protected area, the decontamination chamber, the decontamination shower or from laminar safety cabinets must be all decontaminated before the final discharge preferably through a heat treatment and often their ph scale needs to be corrected. The water coming from the showers and the personnel toilets can be directly discharged into the sewer system without any treatment.
  • Emergency power system: for example
  • an engine generator or uninterruptible power supply.
  • Drain pipes for safety discharge: the floor drain must be compliant with the containment measures as well.

It is necessary to remember that especially for the BLS3 the maximum containment laboratory must be placed in a separate building or in a clearly designated area inside a safe building. The entrance and the exit must have a filter system with interlocking airtight doors. The personnel working in the maximum containment laboratory must take a shower right after they finish working. A negative pressure must be kept in the structure as it happens for the BSL3 but both the supplied air and the extracted air must be filtered with HEPA filters.


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