Two commonly used aerosol equipment solutions are the Madison Chamber and the dual-sided Class III aerosol exposure glovebox with a docking mobile animal transfer cart. The Madison Chamber is used for animals ranging from mice to rabbits and the dual-sided unit is used for small animals and non-human primates.
The Madison aerosol exposure chamber was developed by the University of Wisconsin in 1970 as a stand-alone system designed for total body exposure of animals as small as mice or as large as rabbits. The chamber, which can hold up to 90 mice, allows researchers to simultaneously infect large numbers of animals. It is essentially a pressure vessel that contains a nebulizer, which is filled with a particular agent that is drawn through the chamber to completely expose the animals. During exposure, the aerosol is contained within the system and a purge cycle following aerosolization reduces lingering agents. The chamber, designed for specialized BSL-3 and BSL-4 labs, is being used today to study tuberculosis, bioterrorism agents, anthrax, and any research that requires the infection of a large number of animals.
As a stand-alone system, the chamber poses potential exposure risks to researchers working with pathogens. The chamber was not designed to interface with a Class II or III glovebox. However, the Baker Co. of Sanford, Maine, developed an interface consisting of a Class III glovebox and a Class II biological safety cabinet to provide enhanced containment. Numerous modifications must be made to include the interface, but the changes can be made without altering the aerosol dispersion characteristics of the unit.
“There are only about 40 or 50 of the Madison Chambers being used in the world today and there have been reported cases of researchers being infected when they opened the stand-alone chamber,” says Mark Zarembo, custom products division manager at the Baker Co. “Only about six of the chambers that are in use have the interface with the glovebox and biological safety cabinet.”
When effectively integrated with the glovebox and biological safety cabinet, the chamber provides containment in the event of an accidental spill, provides uniform and contained distribution of aerosols, provides clean air to the work space with significant increases in air purge rates, and provides a means of animal transfer between the chamber and the microisolator cage in a Class III biological safety cabinet environment. The Class II cabinet is used for safe, efficient cage changing, while a wall pass-through allows cage changing in labs separate from the exposure lab. Ports provide a vehicle to introduce gaseous decontamination agents.
“The interface allows researchers to work under safer conditions,” notes Zarembo. “In the old days, animals might be brought right back into a room after being in the chamber and there was the potential for infection. The integrated containment system is not foolproof, but it raises the level of protection. There are inherent dangers because researchers are purposely generating large quantities of aerosol, making it crucial to implement safety controls and to use the right equipment to make the environment safer.”
Baker also developed the dual-sided Class III aerosol exposure glovebox with the mobile animal transfer cart and docking station. It enables researchers to move animals to and from holding areas while maintaining containment by using a HEPA-filtered, battery-powered cart and docking directly to the exposure glovebox. It also allows two or more researchers to manipulate the animals. This equipment is used mostly for working with non-human primates.