There are two main types of isolation chambers: positive pressure and negative pressure. In general, positive-pressure isolation chambers are used to ensure that specified-pathogen-free (SPF) laboratory animals housed in the chambers are protected against outside contaminants (Hurni, 1981; Clough et al., 1995) . Negative-pressure isolation chambers are used with infectious animals housed in the chambers to prevent migration of hazardous contaminants to the outside (Wathes and Johnson, 1991) .