Many research animals require isolation. In the past, cage-transfer protective equipment was designed primarily to prevent contamination of such animals. While that concern has not diminished, recent events have focused attention on protecting lab workers as well. In some cases, contamination has spread from lab animals to attendants, and in many cases, occupationally-induced asthma has been linked to excessive exposure to animal residue. This paper surveys some of the literature describing passively-transmitted hazards which may be created when animals are manipulated, when they are transferred, or when their cages are cleaned.