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THE USE OF HYDROGEN PEROXIDE VAPOUR (HPV) IN  THE DECONTAMINATION OF ROOMS, BIOLOGICAL SAFETY CABINETS AND OTHER ENCLOSURES

Historical Information and Risk Assessment.

In 2005 Critical Certification Pty. Ltd. in the interests of both clients and staff took a stand against the use of Formaldehyde to fumigate Biological Safety Cabinets.

Formaldehyde is now a known carcinogen and its use is unpleasant for any personnel involved, but also dangerous due to its explosive potential and irritant nature.

The standard method used, including the use of silicon oil, was often adapted and used by insufficiently trained staff.

Additional, the use of kits where an uncontrolled, vigorous exothermic reaction between potassium permanganate and formalin can be dangerous, when not controlled and monitored safely.

The use of formaldehyde is now prohibited or very restricted in many countries, including Australia and New Zealand, with regulations being reviewed and limits reduced constantly.

The use of hydrogen peroxide also poses some risks, but with the systems’ checks and measures in place, using a proprietary system, the risks are almost nil. An additional benefit is that the by-product of a HPV decontamination is (in small concentrations) water and oxygen.

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Training and Experience.

Our key staff undertook comprehensive training at Bioquell (Andover, England) and taught how to perform  successfully decontamination using Hydrogen Peroxide Systems. Critical Certification was then able to introduce the HPV technology to Australia.

Documented use of HPV.

The use of HPV as a decontaminate  is well documented, and when undertaken correctly offers a more safe and also effective means to achieve decontamination. Hydrogen Peroxide can be difficult, however, to effectively decontaminate as the vapour is not a gas and has different characteristics. The suggested efficacy demonstration for Formaldehyde decontamination is using four-log Biological Indicators.

In 2006 Critical Certification submitted Type Tests using six-log USP Biological Indicators on all common makes of Biological Safety Cabinets in Australia to the OGTR. Following OGTR’s assessment, approval was gained for our process.

With our submitted type tests to OGTR we have reproducibly demonstrated a six-log kill, thus well exceeding the required standards.

This difference is reassuring and is becoming more important with the emergence of Multi-Drug Resistant organisms that many of our clients use. The technology, however, is not invincible and even leading authorities on decontamination technologies such as the Health Protection Agency at Porton Down (UK) will caution that the use of HPV in decontamination must be carefully undertaken to ensure optimal results. 

Unlike Formaldehyde and Chlorine Dioxide, (the only two true gaseous fumigants) HPV is less penetrative. Due to this physical fact, the correct use of the decontamination equipment is critical.

Types of BSC Decontamination.

With the HPV technology, two types of decontaminations are offered: 

Workzone Decontamination 

This process is a decontamination within the actual workzone of the BSC. This means that the contaminated area of the BSC in contact with the test apparatus used is decontaminated prior to testing. This kind of decontamination is used where testing is routine, and there are no reported problems and no problems are anticipated.

Without workzone decontamination of a BSC, our technicians are at risk from potential exposure to agents used and also risk contamination of equipment that will subsequently be used elsewhere. The volume of 30% Hydrogen Peroxide is determined by cabinet volume, and this is important. A 1.2 metre cabinet requires 15ml and a 1.8m cabinet requires 25ml. Using less is, as our validations have shown, insufficient to decontaminate the work zone.

The cabinet is usually able to be tested within 2.5 hours of the process beginning.

Full Decontamination

This process is used where a problem is known or suspected (such as a paper towel in the fan, complete fan failure, rattle or high filter pressures. The entire interior of the cabinet, including the plenum (the contaminated area inside of the cabinet, fans and filters) are decontaminated. This process requires a higher volume, fine technique and also a much longer safe clearance time due to the higher levels of hydrogen peroxide used. For a 1.2m cabinet the volume of 30% hydrogen peroxide required is 65ml and for a 1.8m cabinet 155ml is required.

Decontamination Efficacy.

To achieve a six-log kill in a Biological Safety cabinets requires a balance of the following factors.  

1. Integrity and Brand of Hydrogen Peroxide

The integrity of the reagent is critical. Hydrogen peroxide is a very unstable substance and conditions in Australia mean that its portability is limited. We purchase the highest analytical grade available and store it refrigerated and out of light. Our technicians dispense peroxide freshly for use into the dark proprietary bottles on a daily basis. Hydrogen Peroxide is not stored in the vehicles, and is transported onto client sites using small Eskis. No large quantities of the 30% Hydrogen Peroxide are bought onto your site without prior notification.

2. Concentration of Hydrogen Peroxide Vapour

15ml of a 30% Hydrogen Peroxide is used for standard 1.2m workzone decontaminations.

3. Circulation

Since HPV is not a gas, but a vapour, the vapour requires circulation. Factors such as the set up of the apparatus is critical, particularly where a full decontamination is required. Critical Certification use chemical indicators with every decontamination, for an immediate indication that our process has been initiated and completed as expected.

We are the only service provider that has validated our processes with the OTGR. Client site process validation is available as an option on request. 

4. Contact time

An important part of the decontamination is not only the correct concentration of hydrogen peroxide, but also the time it has to contact the contaminated surfaces. Our machines are programmed with the contact time determined according to our efficacy data. 

5.Clearance Safety

Hydrogen Peroxide is not safe above 1ppm for long term exposure. Our policy is that the levels in the cabinet will not exceed 1ppm prior to discharge back into lab air. This is monitored using calibrated Portasens equipment. A standard workspace decontamination is not possible to be completed in less than 1.5 hours under any circumstances.

Critical Certification Pty Ltd offers this service for the following:

  • Biological Safety Cabinets
  • Pharmaceutical isolators
  • Incubators
  • Animal Racks & Cages
  • Other small Laboratory Equipment

In addition, Critical Certification Ptl Ltd also offers a full Room Decontamination Service for rooms as follows

  • Cleanrooms
  • Physical Containment Laboratories
  • Operating theatres, wards and isolation rooms
  • Most Sterile Environments 

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