Dry Vapour Decontamination Technology

Dortek Ltd

The term "Dry Vapour" is used to describe a vapour made up with droplets of sizes below 2µm; in the past droplet size consistency was difficult to achieve but technology has now provided equipment that will deliver just that. Using nozzles made to precise specifications and employed as part of a balanced atomising process, liquids are dispensed meeting the droplet size criteria.

When generated the droplets that make up the vapour have certain characteristics: they do not settle or disperse on contact with surfaces, so no wetting occurs; and they do not disintegrate but keep their shape until evaporation takes place.

Dry Vapour Decontamination Technology

Dortek has looked at all aspects of the process and has listened to end user views. The result of this is the development of the Vapour Disinfection System (VDS). Dortek believe this new dry vapour decontamination technology meets all the criteria based on the feedback from the medical and science industries.

The physics and science of the dry vapour is far more complicated than this brief overview suggests - but, as the name suggests, it is dry. From a practical point of view it is used in applications where it dispenses liquids in an area without giving rise to the wetting issues of traditional fogging procedures.

Cycle Time

Keeping to the ethos of basics and simplicity, Dortek has developed a system that will dispense liquids both into small volumes such as cabinets, as well as in large areas in which the only restriction on size would be the amount of compressed air available. Another factor is that, no matter how large the area, the cycle time from start of gassing to end of "kill time" is more or less constant; variables that affect the cycle time are feed air volume and the method of venting the vapour.

With the VDS system the preferred liquid is dispersed through single or multiple nozzles (calculated on volume to be treated) in a fine plume of droplets that have a consistent size depending on the application but are <2µm. These then act according to the Brownian motion (the erratic and constant movement of tiny particles when they are suspended in a fluid or gas).

Process Control

The process is controlled in real time by measuring the humidity levels; a number of remote sensors are placed within the area and monitored. Control of sterilant discharge is from outside the area and each nozzle is independently managed. This means that the humidity in the area can be balanced as the sterilant is introduced, which avoids optimum humidity being compromised in parts of the area and prevents wetting taking place.

Factors that affect the flow of the vapour and thus the performance are the configuration of the area (how many rooms, shape of area and position of equipment) and the displacement volume of equipment left in the area. Monitoring the humidity and controlling the process with the sensor information leads to an effective and dry process.

The sensors also confirm that the area is sealed as after the vapour discharge part of the cycle has taken place the reaction time for the vapour is entered, a drop in the humidity will indicate that the fog is escaping from the area.

The third and final part of the cycle is the evacuation of the vapour. This is carried out and then monitored with the bellows and detection tube method. When the safe level is achieved (1ppm hydrogen peroxide and 10ppm acetic acid) the area can be occupied.

The process is validated through the use of biological indicators (Geobacillus stearothermophylus); these are placed in the room and exposed to the disinfection, after which they are cultured in a suitable media and under appropriate recovery conditions as specified by the manufacturer. If no growth occurs, the disinfection process is deemed to have worked.

Dortek carries out single and multi service contracts as well as supplying systems. Our systems are:

  • Aerosol based and powered by compressed air
  • Simple with no moving parts
  • Quick - the process can take as little as two hours to decontaminate a facility
  • Flexible, in that it will dispense a diverse range of liquids.

The process penetrates normally inaccessible areas without condensation issues so electrical equipment, for example, can remain in the facility during the decontamination cycle.

The equipment can be:

  • Mobile - useful when a number of areas need to be treated within a facility
  • Fixed - ideal for large areas which need to be treated regularly and quickly
  • Bespoke - designed to the customers specifications and parameters

Mobile & Fixed Systems

The process is used to reduce the risk of contamination not only in cleanrooms but in any facility that requires decontaminating. The vapour-dispensing nozzles, adapters and feed pipe are the only parts of the system placed in the area to be treated.

Hydrogen Peroxide / Peracetic Acid Disinfectant

Vapour- dispensing nozzle

Dortek's preferred sterilant is a hydrogen peroxide/peracetic acid disinfectant which is an effective bactericide, virucide and sporicide that has validation and efficacy when delivered by the dry vapour method; it is also biodegradable.

For many years formaldehyde has been the biocide of choice because it works and can be applied as a gas - and generally speaking people are resistant to change.

But now there are alternatives in both biocides and their methods of application, and these alternatives do not have the risks and issues associated with formaldehyde and are more user friendly.

Dry vapour is an alternative way of application and Dortek believe it ticks all the boxes that a responsible industry is looking for.

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