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Formalin Vaporizer
Chapter 3 – Decontamination Process
3.1 Formalin/Paraformaldehyde Decontamination
Typically the decontamination is performed using formalin gas by either vaporizing 37% formalin solution or by
de-polymerization of solid paraformaldehyde.
Despite its widespread usage for decontamination, formalin presents the following health risks:

External contact can cause irritation to skin, eyes, and mucous membranes.

Inhalation in small concentrations can cause coughing, nausea, and diarrhea.

Inhalation in large concentrations can cause convulsions, coma, and death.

Long term exposure can cause cancer.
Although the Permissible Exposure Level (PEL) for formalin is 0.75 ppm, many scientists believe that there is no
safe level of carcinogen exposure to humans. Therefore, typically the room must be evacuated when the
decontamination process is performed, which leads to lab down time.
The use of formalin decontamination also has other disadvantages:

The process is time-consuming.

The certifier needs to pulse the BSC fan to circulate the formalin vapor. This can dislodge the tape
holding the plastic sheet covering the exhaust filter.

Due to excessive residue extensive cleaning must be done after decontamination and before use.
The formalin decontamination process can require an extended period of time as outlined below:
According to OSHA [Occupational Safety and Health Administration (USA)], formaldehyde Short Term Exposure
Level (STEL) is 2 ppm for 15 minutes exposure, 4 times a day, minimum of 60 minutes in between exposures.
Any additional local safety regulations should also be observed. Personnel should be given adequate training.
The following links provide general guidelines on formaldehyde safety:

Regulations (Standards - 29 CFR) Formaldehyde - 1910.1048, Occupational Safety and Health
Standards, OSHA (Occupational Safety and Health Administration), U.S. Department of Labor:
http://www.osha.gov

OSHA Formaldehyde Fact sheet (PDF format)
http://www.osha.gov/OshDoc/data_General_Facts formaldehydefactsheet.pdf
No. Process Time
1 Set-up & sealing the BSC to make it air tight 1 hour
2 Formalin vaporization ½ hour
3 Formalin contact time to obtain target log of 4-6 kill 8 – 10 hours
4 Ammonia vaporization to neutralize formalin ½ hour
5 Ammonia contact time to neutralize formalin 2 hours
6 Exhausting the ammonia residue 1 hour
7 Tear-down & cleaning the (substantial) residue 1 hour
TOTAL without ammonia neutralization 10½ – 12½ hours
TOTAL with ammonia neutralization 14 – 17 hours
Ammonia is used to neutralize formaldehyde. OSHA prescribes the ammonia STEL is 35 ppm for 15 minutes
exposure, 4 times a day, minimum of 60 minutes in between exposure.
Due to the adverse health effect of formalin gas, its use has been banned in Germany, Austria, and
Switzerland. Other European countries are expected to follow suit. Two primary candidates to replace formalin
decontamination are chlorine dioxide gas and hydrogen peroxide vapor.