Equipment Bio-Decontamination Service (EBDS)

As more and more companies change their decontamination protocols from traditional methods such as formaldehyde fumigation, BIOQUELL has seen a positive upturn in the need to provide an alternative which offers a safe, easy to use and highly effective method in the form of hydrogen peroxide vapour (H2O2). This article looks at the reasons for this change and the various applications of BIOQUELL's Clarus technology, specifically involved in the decontamination of laboratory equipment.

With the use of aldehydes becoming increasingly unacceptable throughout the world due to efficacy and safety issues, hydrogen peroxide vapour provides a safe and effective alternative bio-decontaminant, that achieves significant process time advantages and a high level of proven efficacy.

Hydrogen peroxide vapour (H2O2) is non-carcinogenic, safe and efficacious against a wide range of viruses, bacteria and moulds offering clear advantages over other techniques such as formaldehyde, peracetic acid fogging or the nebulising of toxic biocides. H2O2 vapour breaks down under catalytic action making it environmentally friendly, leaving no residues unlike many other biocides.

EBDS Technology
BIOQUELL has introduced the Equipment Bio-Decontamination Service (EBDS), taking advantage of the latest developments in H2O2 gassing technology for the routine and emergency decontamination of enclosures, Biological Safety Cabinets, Incubators and other laboratory equipment. With increasing numbers of new and existing Service Contract customers taking up the option of EBDS, BIOQUELL is demonstrating the many advantages of this unique technology on a daily basis.

How EBDS is Implemented
BIOQUELL provides EBDS using the Clarus® S H2O2 gas generator based on patented Clarus technology developed by BIOQUELL. The equipment is compact, mobile and can easily be moved around between locations. All of BIOQUELL's service personnel are fully trained in the procedure and associated safety requirements. The Clarus S suite has been designed to serve the markets need for a compact, fast and effective system for bio-decontaminating laboratory equipment. It is simple to set-up and connects easily to a wide range of equipment.

Fumigation of a BIOQUELL Microflow Cabinet using the Clarus S system

The Bio-Decontamination Cycle

The Clarus S consists of a Vaporiser, Internal and External Catalyst linked by the Control Panel. There are three important phases that make up the decontamination process:

1) The Gassing Phase
A 30% w/w solution of hydrogen peroxide is pumped onto a hotplate in an air stream and is 'flash evaporated' thus producing the hydrogen peroxide vapour. The vapour stream is distributed around the equipment using a secondary fan at an elevated temperature. As the vapour generation process continues the concentration of the vapour in the enclosure increases until the vapour's dew point is achieved.

2) The Dwell Phase
As the dwell point is reached the H2O2 vapour starts to settle onto surfaces, forming micro-condensation and being absorbed through any filters so that complete microbiological inactivation is achieved. It is the deposition of hydrogen peroxide condensate and release of free radicals that causes very rapid bio-deactivation. The level of condensation needed to achieve bio-deactivation is very small and cannot typically be seen with the naked eye. However if the gassing process is allowed to continue, visible condensation may eventually be seen.

3) Aeration
When an appropriate contact time has been achieved the Clarus will switch into 'aeration' mode. During aeration H2O2 is recycled and catalytically converted into its component parts of water and oxygen by passing through activated carbon, making it safe to exhaust into the room or atmosphere. The process is residue free:

The external catalyst performs two main functions. During the gassing and dwell phases of the cycle it holds the enclosure under a slight negative pressure ensuring that there is no possibility of a leakage occurring. This is very important as the normal working of the laboratory is unaffected by the service. The internal catalyst is used only during the aeration phase of the cycle to assist in reducing the H2O2 concentration to the Long-Term Exposure Limit (LTEL) of 1 ppm. For a more scientific process explanation please see "Theory and Practice of Hydrogen Peroxide", by Dr David Watling another BIOQUELL article on this site.

Hydrogen Peroxide Vs Formaldehyde
Formaldehyde vapour has been used for the bio-decontamination of cabinets and laboratories for over 100 years, yet the efficacy of the process remains controversial (1) and there are many practical difficulties and toxic hazards associated with formaldehyde vapour. It acts as an alkylating agent, inactivating micro-organisms by reacting with proteins and nucleic acid bases. Formaldehyde must dissolve in sufficient concentrations in the immediate vicinity of the micro-organism in order to be efficacious.

Carcinogenicity
Formaldehyde vapour is carcinogenic to humans (2). It has a pungent smell, which is offensive to operators and is detectable to operators below 2ppm. Formaldehyde also forms residues on surfaces, which have to be manually wiped down. This process is slow and unpleasant for operators. Hydrogen peroxide vapour is odourless and decomposes to oxygen and water vapour so leaves no problematic residues.

Decontamination with hydrogen peroxide vapour is much safer and more environmentally friendly than formaldehyde decontamination, especially when the decontaminant vapour is vented into the atmosphere.

Fire Hazard and Risk of Explosion
Formaldehyde vapour is classified as extremely flammable and the vapour mixes well with air resulting in an explosive mixture (3). This is due to the 50°c flashpoint for 37% formaldehyde. Further, formaldehyde is known to react violently with strong oxidants, alkaline materials and toxic vapours and gasses may be released.

Due to the flammability and reactivity of formaldehyde, fires have been known to start during formaldehyde-based decontamination.

Tests carried out by BIOQUELL have also proven that hydrogen peroxide vapour decontamination of an enclosure using Clarus technology is neither flammable nor explosive. Hydrogen peroxide vapours can only be ignited in the presence of a spark at temperatures in excess of 150°c and at 260,000 ppm or 26 mole % (9).

High powered ignition source within an enclosure at 961 ppm.

Efficacy
Studies have shown that the biological efficacy of formaldehyde as a vapour-phase decontaminant is limited, especially compared to the broad biological efficacy of hydrogen peroxide vapour. For example, the Centre for Applied Microbiology and Research (CAMR) conducted a comparative investigation between formaldehyde and HPV for the decontamination of a biological safety cabinet (4). This study showed that HPV is more efficacious and reacts quicker than formaldehyde.

Survival curves for biological indicators exposed to (a) hydrogen peroxide vapour and (b) formaldehyde in a class II microbiological safety cabinet

Simplicity and Speed of Process
Investigations have also shown that the biological efficacy of formaldehyde is greatly dependent upon variables that are difficult to control in practice, such as relative humidity and temperature (1,5). The larger the enclosure, the more difficult such variables are to control.

Variations in temperature and relative humidity are not as essential to the biological efficacy of hydrogen peroxide vapour (6). Therefore, hydrogen peroxide vapour is more practical for the decontamination of large enclosures.

Absorption and Out-Gassing
According to the US Environmental Protection Agency (EPA), formaldehyde is absorbed into materials and 'out-gasses' for an extended period after the cycle has been run. Though there is no qualitative data available, the same source describes hydrogen peroxide out-gassing as 'rapid' (7).

Penetration
Formaldehyde has poor penetration capacity (1,8). This limits the practical application of formaldehyde, especially for the decontamination of safety cabinet filters. Formaldehyde was found to be ineffective at decontaminating Geobacillus Stearothermophilus biological indicators placed throughout a Class II safety cabinet.

In contrast, full bio-deactivation was achieved using hydrogen peroxide vapour when BI's were positioned around the working area, back duct, plenum and air-offside of the exhaust HEPA's (4).

Time
Due to limited penetration and slow microbicidal action time, at least 12 hours exposure is recommended for formaldehyde decontamination. Figure 3 highlights the relatively rapid microbicidal action time of hydrogen peroxide vapour.

Further, it typically takes over 24 hours to completely vent formaldehyde vapour (7). Therefore, any area that is decontaminated is out of action for at least 36 hours not including the time taken to manually wipe down formaldehyde residues. In contrast, hydrogen peroxide vapour cycles typically last two hours in total.

Material Compatibility
Hydrogen Peroxide has excellent material compatibility properties. During BIOQUELL's extensive testing, sensitive electronic equipment was subjected to 860 gassing cycles resulting in zero degradation of functionality or appearance. Furthermore as an example of the material compatibility of the process, sensitive and expensive hospital equipment is regularly bio-decontaminated across the world.

In addition to electronic equipment, hydrogen peroxide has excellent general material compatibility, as detailed in BIOQUELL's material compatibility document available on request.

Validation
High-level disinfection of small and large volumes can be rapidly achieved in a repeatable and validatable manner using the Clarus® range of equipment. Generally a 6-log reduction in bio-burden is achieved and this is typically validated using a biological challenge such as Geobacillus Stearothermophilus spores, which are chosen specifically for their known resilience.

(For more information on this subject please refer to another article on this site written by Dr D Watling, "Sporicidal Gassing").

When the correct conditions have been reached, bio-inactivation is very rapid with D-values below two minutes so 6-log bio-burden reduction on spores is readily obtainable. H2O2 vapour is very effective against spore forming organisms such as bacteria and fungi and has a high level of efficacy on yeast and virus.

Independent research commissioned by BIOQUELL shows that H2O2 vapour is effective against anthrax spores (B. anthracis). Further information on the biological efficacy of H2O2 is available in another article on this site by Jon Otter and Rachel Jarman-Smith or from BIOQUELL on request.

Applications
The Clarus S is suitable for the bio-decontamination of a wide range of equipment and enclosures. The picture opposite is one of the many cell-culturing machines from "The Automated Partnership" (TAP). BIOQUELL work in conjunction with TAP in providing a decontamination service to customers worldwide.

Standard makes and models of equipment have been "type tested" by BIOQUELL and can usually be bio-decontaminated without further investigation; other equipment is "type tested" by mutual arrangement.

It is becoming increasingly common for manufacturers to recommend bio-decontamination with HPV.

Conclusion
Hydrogen peroxide vapour is a rapid, residue free alternative to formaldehyde, which has proven biological efficacy and relatively few health and safety issues which can effectively bio-decontaminate any enclosure, ranging from a biological safety cabinet to infinitely large buildings.

BIOQUELL's innovative approach has enabled a unique level of service to be provided.

The service organisation is able to draw upon the significant experience and expertise within BIOQUELL's substantial technical and R&D departments to provide services to the private and public sectors. Preventative maintenance contracts from BIOQUELL can be tailored to suit customer's specific requirements.

This service is supported by BIOQUELL's extensive infrastructure and network of trained engineers.