Dear Sirs

Good day. I have a problem when i sterilize surgical instruments in a formaldehyde sterilizer: The instruments have some formaldehyde particules on their bodies. knowing that the formaldehyde cycle is at 55 degree celcius, i just want to ask you sirs, is there any problem with the sterilizer, ot is it the type of the tablets (i use paraformaldehyde tablets with a PH 5.5 and a flash point 70 degree clecius)?
thank u for your time.

Imad MOSLEM
LEBANON

Dear,

Condensation and polymerisation of formaldehyde on instruments is often a problem of temperature, cold surfaces and/or a problem of presence of water on the load.
The maximum achievable concentration of formaldehyde in gaseous form (mg/l) above paraformaldehyde is:

• at 50°C: 10 mg/l
• at 60°C: 21 mg/l

I recommend you to check:

• the theoretical concentration of formaldehyde in the chamber after sublimation,
• the temperature in the chamber during preconditioning and sterilization,
• the amount of water that's brought in the sterilizer on the instruments or during preconditioning.

Good luck,
Wim Renders

p.s.
I advise you also to check the reproducibility and thus the reliability of the method you're using. See also questions Q00125, Q00112, Q00077 and Q00067.

Imad,

The process you describe can, in general, not be accurately controlled. Moreover, dry formaldehyde is not a very effective sterilant. Modern formaldehyde sterilisers use a combination of low temperature steam and formaldehyde (LTSF), where the feed of the sterilant can be controlled. PrEN 14180 on LTSF-sterilisers has been published and accepted. I expect the EN 14180 to go out for formal vote in Autumn 2002. This standard also describes a method to test for residual (par)formaldehyde. The test device is a filter disk. paper is known to retain a lot of formaldehyde.

Arjan van Drongelen
Dutch National Institute for public Health and the Environment (RIVM)

Any opinions expressed in the e-mail are those of the individual and not necessarily the RIVM.