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LTSF sterilization processes

The low temperature steam formaldehyde (LTSF) process is not a typical gas sterilization process but a modified steam sterilization process. Details of the sterilizer specifications are available in the standard EN 14180. This process is divided into the following consecutive steps:

(A) Conditioning phase

  • - air removal
  • - steam penetration
  • - condensation of steam to water on all surfaces to be sterilized

(B) Formaldehyde saturation

  • The condensate on the surfaces must be saturated with formaldehyde gas (gas: liquid concentration = 1:10.000 in equilibrium), therefore a long convection and/or diffusion phase is required until equilibrium is achieved

(C) Sterilization

  • Different sterilization times depending on the temperature and the formaldehyde concentration and on the load configuration are required

(D) Formaldehyde desorption

  • Elution of the formaldehyde with steam/water

(E) Drying

  • Cyclic aeration and deaeration under sterilization temperature conditions

(A) Conditioning phase

  • All processes have in common that they use a fractionated vacuum to carry out the conditioning phase (A) which assures air removal, steam penetration and condensation of water on all surfaces. Pressure differences in formaldehyde sterilization processes are quite low. The possible lower pressure value is depending on the quality of the pump and the cooling water temperature (approx. 3