30
Chapter 6 -
Decontamination
BSC decontamination should be performed in any of the following eventualities:
•
Before replacing the exhaust/downflow filters or blower.
•
Before accessing the contaminated negative or positive plenum of the BSC.
•
In case of an accidental spillage that might have contaminated any of the inaccessible surfaces.
•
Before performance validation and re-certification.
•
Before BSC relocation.
•
Before any procedures mandated by user’s risk assessment.
Appropriate Personal Protective Equipment (PPE) per user’s risk assessment that may include gloves, gown,
and respirator with filter suitable for the decontamination gas/vapor must also be used by the certifier or any
other qualified personnel performing the decontamination.
Esco can provide the formalin vaporizer (FV-001) and decontamination bag needed for the decontamination
procedure.
The information provided in this section does not construe a final advice on how decontamination must be
carried out. Appropriate personnel including the safety personnel in the facility must be consulted and
adequate risk assessment must be conducted to ensure the safety and efficacy of the decontamination
procedures.
6.1.
Decontamination Agents
6.1.1.
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 gas 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.
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
format).
Available
at:
http://www.osha.gov/OshDoc/data_General_Facts formaldehydefactsheet.pdf
Summary of Contents for Class II
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