There are usually four levels of laboratory containment (based on WHO classifications) which are defined for pathogenic organisms (not just for genetically modified organisms) and are based on the hazard classification described elsewhere.

Level 1 is the lowest level or containment, and requires no extra precautions above those required for good microbiological practice. In general, this means that(12)

• Laboratory personnel must be instructed in the procedures used in the laboratory.
• The laboratory should be easy to clean. Bench surfaces should be impervious to water and be resistant to acids, alkalis, solvents and disinfectants.
• If the laboratory is mechanically ventilated, an inward air flow into the laboratory should be maintained by extracting room air to the atmosphere.
• The laboratory must contain a wash handbasin or sink that can be used for hand washing.
• The laboratory door should be closed when work is in progress
• Laboratory coats or gowns should be worn in the laboratory and removed when leaving the laboratory suite.
• Eating, chewing, drinking, smoking, storing of food and applying cosmetics must not take place in the laboratory.
• Mouth pipetting must not take place
• Hands must be disinfected or washed immediately when contamination is suspected, after handling viable materials and also before leaving the laboratory.
• All procedures must be performed so as to minimise the production of aerosols.
• Effective disinfectants must be available for immediate use in the event of spillage.
• Bench tops should be cleaned after use
• Used laboratory glassware and other materials awaiting disinfection must be stored in a safe manner. Pipettes, if placed in disinfectant, must be totally immersed.
• All waste material which is not to be incinerated should be rendered non-viable before disposal.
• Materials for disposal must be transported without spillage in robust containers
• All accidents and incidents must be recorded.

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The conditions for higher levels of containment, where the organism is considered a pathogen, are listed in the guidance note (see footnote ). For level 2, the major addition are the need to ensure that access to the laboratory is restricted to those needing to enter; that there be adequate space for each worker (at least 24 m³); an autoclave must be readily accessible and all waste materials must be made safe before disposal either by autoclaving or by incineration.

Table 1:

Summary of Laboratory Containment Requirements(13)

	Level 1	Level 2	Level 3	Level 4
Laboratory suite: isolation	No	No	Partial	Yes
Laboratory: sealable for fumigation	No	No	Yes	Yes
Ventilationinward airflow/ negative pressure	Optional	Optional	Yes	Yes
through safety cabinet	No	Optional	Optional	No
mechanical: direct	No	No	Optional	Yes
mechanical: independent ducting	No	No	Optional	Yes
Airlock	No	No	Optional	Yes
with shower	No	No	No	Yes
Wash handbasin	Yes	Yes	Yes	Yes
Effluent treatment	No	No	No	Yes
Autoclaveon site	No	No	No	No
in suite	No	Yes	Yes	No
in lab: free-standing	No	No	Optional	No
in lab: double-ended	No	No	No	Yes
Microbiological safety cabinet / enclosure	No	Optional	Yes	Yes
Class of cabinet / enclosure	-	Class I	Class I/III	Class III

There will be risks to the environment for contained use of modified organisms as well. The escape of modified organisms used in laboratories should be of little significance as they should have been disabled so that, in the event of escape, they will be unable to survive. However, the assumption has been that the only concern is risk to human health and safety. The risk assessment has been predicated on this, and the possibility that the organism may be a danger to other organisms within the environment has not been fully considered in the discussion. The concept of the 'environment' which includes land, air and water as well as other organisms and humans, is so broad when compared to the enclosed environment of the laboratory that is it difficult to define a clear step-wise approach to risk assessment. The risk assessment must try to consider all possibilities of what could go wrong, and attempt to ensure that these cannot happen, largely through the design of the organism being used. Methods for retrieving the situation should an organism escape from containment become important, and need to be planned at the outset rather than relying on the containment procedures to work. This is particularly important where the organism is a Level 1 organism as it will not infect humans, but if it escapes could be disastrous to plants, insects or other animals.

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