Few topics seem to generate more confusion than respiratory protection related to HDs. Most nurses are familiar with N-95 respirators. These devices, (which must be fit tested annually) are designed to protect against aerosols and particles. (Refer to NIOSH for additional information on respirators.) The confusion occurs when the differentiating between aerosols and vapors.
Aerosols are a suspension of solid or liquid particles. Vapors, on the other hand, are gasses typically generated from a liquid. Two familiar examples are gasoline (a liquid with an odor) and perfume (a liquid with a fragrance).
There is very limited data on which HDs vaporize at room temperature. However, two studies* have indicated vaporization can occur with 8 drugs. To understand which type of protection is required for vapors, it is useful to trace the genealogy of these drugs.
8 drugs that vaporize at room temperature
Connor, T, Shuts, M, & Fraser (2000). Mutation Research, 470, 85-92; Kiffmeyer, T., Kube, C, Opiolka, S, Schmidt, K., Schoppe, G., & Sessink, P. (2002), The Pharmaceutical Journal, 268, 331-337.
As an alkylating agent, Cyclophosphamide is chemically related to nitrogen mustard which evolved from mustard gas used in WWI. Therefore, protection from these drugs requires similar (but newer) technology. The options are a full-face organic vapor [OV] combination canister respirator or a PAPR (powered air-purifying respirator) with an OV cartridge. NIOSH has an excellent document describing respirators, which can be found here.
3M TR600 PAPR with OV cartridge
PAPRs have an advantage in that they do not require annual fit testing and provide excellent full-face protection during spill cleanup. They are also less prone to causing claustrophobia and are more comfortable for extended periods of time (as might be required with a larger spill). Not all PAPRs are able to handling the airflow for an OV cartridge, so check with the manufacturer. Of course PAPRs cost considerably more than full-face respirators, but aside from the disposable hoods, they are reusable and can last many years so the cost can be spread out.
Combi Respirator with OV canisters
Full-face combi respirators are markedly different from the N95 respirators most of us are familiar with. They look similar to gas masks used in WWI, and like other respirators, require a tight facial fit to perform effectively. While more expensive than N95s, they are considerably less expensive than PAPRs.
More Unanswered Questions
Unfortunately, there is no data for the dozens of HDs approved in the last 30 years. According to Tom Connor, author of one of the above papers, vaporization studies are difficult to conduct in laboratory settings and almost impossible in clinical environments.
Also unknown is the influence of real-world environmental airflow; vapors pose a higher risk in an enclosed space (e.g., patient bathroom) compared to a hallway, all of which depend on the air exchanges per hour in the facility.