How growth chambers can be used to meet containment standards

Reach in growth chambers and walk-in growth rooms feature precision control of temperature, light, humidity, CO2 and other environmental control variables when compared with field trials and greenhouses. They also deliver containment advantages. According to NIH Guidelines, growth chambers may be used for containment at BL1-P and BL2-P levels under certain conditions, and even for level BL3-P if more stringent conditions are implemented within the building. The USDA's Animal and Plant Health Inspection Service (APHIS) routinely permits the use of a growth chambers, provided the facility meets containment standards and passes physical inspections.

Some containment advantages of growth chambers include:

• ​Year round precision environmental control
• Location flexibility as growth chambers can be placed in multiple locations in a building
  
• Earthquake, weather and vandalism resistance
• Enhanced security
• Equipment maintenance performed outside the containment area
• Exhaust air can be HEPA filtered
• Reduced foot traffic
• Smooth interior surfaces that are easy to clean

Growth chambers or rooms must be located within a containment laboratory, greenhouse headhouse, or dedicated facility—an arrangement referred to as the ‘room within a room’ concept. The larger ‘room’ enhances containment by providing filtered air and runoff decontamination, for example. Growth rooms are also manufactured with a vestibule that provides an additional layer of isolation between the growth area and the larger facility.

As with greenhouses, growth chambers or rooms used for BL3-P and other high containment situations require special features such as HEPA filtration of exhaust air and directional airflow. Read more below about hepa filtration on growth chambers at the New Zealand Biotron and the Morden Plant Pest Containment (PPC 3) facility.

Though standard growth chambers and rooms provide basic containment features, they are not entirely suitable for high containment. While it is possible to direct airflow into a growth chamber to minimize escape of organisms, inward airflow may conflict with the standard airflow design. Flexible barriers around door openings can minimize but not entirely prevent the egress of contained material. Also, a growth chamber is seldom built ‘tight’ enough to restrict all airborne organisms or propagules to a prescribed area within the chamber; therefore material may accumulate in unwanted areas of the unit.

The most practical way to have a ‘tight’ chamber suitable for high containment is to initially stipulate that the chamber meet specific containment standards. It may be possible, in some instances, to retrofit or modify a growth chamber, depending on the chamber style. HEPA filtration units can be installed on growth chamber or growth room exhaust ports. Read more below about hepa filtration on a insectary grow room. Materials within a growth chamber or room may sit on solid trays so that runoff water and debris can be collected and stored for disinfecting or autoclaving. Collecting runoff at the drain may be more problematic, unless the drain is connected to an autoclave, kill tank, or similar disinfection equipment.

In conclusion, growth chambers and rooms offer certain containment advantages. The book entitled “A Practical Guide to Containment” authored by Dann Adair and Ruth Irwin focuses on plant biosafety in research greenhouses, however does provide further information on the suitability of growth chambers and rooms for containment purposes. The book is available electronically by contacting Conviron.

Additional information can be retrieved from the National Institutes of Health, Office of Science Policy on safe containment practices.