EFHSS Questions and Answers - Answer to Question Q00067

I have been asked if I know what the concentration of formaldehyde to use per cu foot or cu meter for the fumigation of OT. This request came from India and while I appreciate this practice is no longer practiced in the west it obviously is over there. It is such a long time since I have seen it done, I am hoping someone may provide the answer or suggest an alternative method of fumigation?????

Derek Henderson
Manager - Sterile Services
Shaikh Khalifa Medical Center
P.O. Box 51900
Abu Dhabi
United Arab Emirates
Tel: +971-2-6331000 Ext. 2383
Fax: +971-2-6313962
Mobile: +971 (0)50 5324928

Hi Derek,

I'll begin with a quote from the 19th century:
"The writer would be distinctly understood as not recommending formaldehyde even when combined with a high degree of heat, as a disinfecting agent upon which reliance can always be placed for the treatment of articles requiring penetration, especially when the exposure is limited to ½ hour. A critical examination of nearly all published experiments with this agent will reveal instances in which the organisms that there was every reason to expect would be killed have survived, and vice versa. It is that occasional unaccountable uncertainty of action that calls forth the warning not to attempt disinfection with formaldehyde"
E.K. Sprague, U.S. Marine Hospital Service, over 100 years ago, 1899.

An aqueous solution of 8% formaldehyde and 70% isopropyl alcohol is a rapid bactercide and tuberculocide.

Formaldehyde has exposure limits: eight hour time weighted average (TWA) of 1 part per million (ppm) and a fifteen-minute short term exposure limit (STEL) of 2 ppm. (Stricter than EtO!) The employer must institute controls to maintain employee exposure below these limits. To fumigate a room will require the person wear a self-contained breathing apparatus (SCBA) with a positive pressure full face mask and the fumes must leave the room through a dedicated exhaust and not enter other parts of the building. As a minimum, specific health hazards the employer must address are: Cancer, irritation and sensitization of the skin and respiratory system, eye and throat irritation, and formaldehyde's acute toxicity.

These folks need to come up with an alternate plan. Not knowing the specifics of the situation there, the materials being disinfected, and what organisms they are attempting to kill, it is hard to make a specific recommendation.

Regards, Pete Bobb BSc, ACE

Dear Derek,

Indeed fumigation is not done anymore since 25 years. In our hospital it is replaced by a proper cleaning of the room followed by disinfection of all horizontal surfaces with an aldehyde based product.

I found in: Hygiene Hospitaliere Pratique, A.Dauphin et J.C. Darbord, ISBN 2-85206-298-4, Editions Medicales Internationales, Paris, some figures about fumigation.
There are basically two methods without human presence:

1. Sublimation and evaporation
2. Aerosolisation.

For both you need special equipment and the room must be cleaned before starting the process.

1. Sublimation and evaporation
   There are three important parameters: temperature, relative humidity and concentration.
   This method is always followed by neutralisation with ammoniumcarbonate or ammoniak to protect patient and personnel.
   • Temperature: Formaldehyde is more stable under 20° C and above 80° C. At room temperature in concentrations above 1.75 mg/L it has tendency of polymerisation.
   • Relative humidity: One should have a rh greater than 70 % to obtain a 5 log reduction of the starting microbial population.
   • Concentration: 4 g/cubic meter is always proposed. But HCHO can only be present as a gas in concentrations below 2 g/cubic meter. So 2g/cubic meter should be sufficient.
   • The overload HCHO will condensate on the walls and other objects. The condensate can't be neutralised and will give problems afterwards.
   The contacttime is 4 hours after total diffusion and of course the room must be hermetically closed.
   The efficacy against viruses is not known.
2. Aerosolasion
   The three parameters here are: particle size, formulation and contacttime.
   This method has the advantage that there are less parameters to control but the particle size is important to obtain the same activity on vegetative forms as the gaseous HCHO.

I hope this information answers your question. Do not hesitate to contact me for more information.

Kind regards,
Wim Renders