GB2380676A

GB2380676A - Microbial decontamination by means of ionised air or other gases

Info

Publication number: GB2380676A
Application number: GB0124481A
Authority: GB
Inventors: Jonathan Hugh Lambert Copus
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-12
Filing date: 2001-10-12
Publication date: 2003-04-16
Also published as: GB0124481D0

Abstract

A method of killing micro-organisms carried in the airflow, or resident on surfaces of systems, by means of ionisation. The systems are those in which the air is moved mechanically, e.g. hand driers or air-conditioning systems. Also disclosed is a method of microbial decontamination of surfaces by a mechanically-propelled stream of ionised gas or mixture of gases. The apparatus consists of a means 3 for generating gaseous ions of either polarity within the system. Such means 3 may consists of a point charged relative to earth or may be an array of such points, strands of electrically conductive material, or an electrically conductive foam. Air is drawn into the system and some of the molecules in the air-stream are ionised by means 3, thereby killing the micro-organisms in the airflow itself. This stream is then used to decontaminate the surfaces of the system.

Description

MICROBIAL DECONTAMINATION IN MECHANICAL HAND DRIERS, AIR- CONDITIONING AND OTHER FORCED-AIR SYSTEMS AND OF SURFACES BY MEANS OF IONISED AIR OR OTHER GASES This invention relates to a means of killing micro-organisms in systems where air is mechanically moved and of killing micro-organisms on surfaces by means of a mechanicallypropelled stream of ionised air or other gases. In one aspect it relates particularly but not exclusively to devices such as hand driers, air-conditioning systems, humidifiers and dehumidifiers, and applies to the decontamination of the airflow and any objects with which it comes into contact, including mechanisms for moving, heating, cooling, drying or moistening the air stream itself, and objects affected by the air stream such as the interior and exterior surfaces of the device or system and hands placed near the outlet of a hand drier. In another aspect it relates to the microbial decontamination by means of a mechanically-propelled stream of ionised air of external objects including but not restricted to surgical instruments and appliances, surfaces in food preparation areas and medical and surgical premises, physiological tissue, foodstuffs and food and drink containers.

It is desirable for all forced-air systems to avoid spreading microbial contamination. Hand driers, for example, should ideally leave hands not only dry but also free from excessive numbers of micro-organisms ; they should certainly not increase the bioburden. The consequence of such an increase might be the spread of infection, particularly in areas where food is handled. However, It is a known problem that the warm, moist conditions inside mechanical hand driers In wash-rooms often provides an ideal breeding-ground for micro-organisms, especially during the relatively long periods between uses. This difficulty is exacerbated when the driers are placed in lavatories, where the count of airborne microbes is naturally increased.

Air-conditioning systems, humidifiers, dehumidifiers, convection and fan-assisted heaters, air cleaners and the like have a similar requirement not to disseminate microbes or provide suitable sites for their rapid multiplication. A failing in this area might lead to a spread of infection by airborne micro-organisms, including bacteria, fungi, spores and viruses. In the case of air-conditioning systems in large office blocks the result can be the rapid spread of diseases such as colds and influenza among workers. Where air is vented to the outside atmosphere the contamination can be spread even further afield, and outbreaks of Legionnaire's Disease have been attributed to microbial infestation of cooling towers associated with air-conditioning systems.

It has been shown that a concentrated stream of gaseous ions can have a marked microbicidal effect, and this technology has been successfully applied in medical equipment designed to disinfect surfaces such as skin or dentine, helping to resolve a wide variety of medical conditions from dental caries to athlete's foot. An example of this type of device is disclosed in Patent Specification no. GB 22469558. - One aspect of the present invention overcomes the abovementioned problems in forced-air systems by ionising some of the molecules in the air-stream and thereby killing the microorganisms in the air-stream itself. This technique can be applied to incoming air, outgoing air, the air inside the apparatus, or any combination of the three. The ion-generating mechanism may be energised only when the air is being mechanically propelled or else permanently, even when the air is relatively still. Microbes colonising the internal and external surfaces of the apparatus are also killed by the impact of these gaseous ions. In some applications ions are also emitted from the system to decontaminate nearby surfaces, such as hands placed near the outlet of a hand drier.

In another aspect of this invention a mechanically-propelled stream of ionised air or other gas or mixture of gases is specifically produced to be directed onto surfaces or objects to

achieve decontamination, as for instance food preparation surfaces, surgical instruments, surgical implants, operating tables, the inside or outside of containers for food and drink, physiological tissue, foodstuffs, and other surfaces or objects where freedom from microbial contamination is important.

In previous examples of the use of gaseous ions to decontaminate surfaces, including physiological tissue, the application of the ions has been without mechanical assistance, relying on relative differences in electrical potential to repel the ions from an emitter and attract them towards a surface across a relatively short distance, typically a few millimetres.

This process has necessitated the rapid removal of local electric charge from the surface being treated to avoid the excessive repulsion of further approaching ions by the build-up of like charges on the surface. A sufficient degree of electrical conductivity has therefore been an essential requirement of the treated surface, and the system has further required a means of conducting away the current resulting from the impact of the ions on the surface to earth, either directly or through apparatus.

As applied to the decontamination of external surfaces, the present invention differs in that it relies on the mechanical propulsion of an ionised air-stream to project the ions onto the surface with sufficient force to achieve decontamination. The requirement for electrical conductivity as a property of the surface to be treated is thereby greatly reduced, and the decontamination of surfaces made of relatively insulative material is therefore made possible. One particular but not exclusive area of application is the sterilisation of the inside of drink bottles, a notable problem because of the need to achieve a combination of long shelf life and safety of the contents without the excessive addition of preservative chemicals which can affect flavour and attract public mistrust and disapproval.

Figure 1 shows one application of the invention to an electrically operated hand drier (1). A high-voltage generator (2) produces a sufficiently high direct voltage, negative or positive

with respect to earth potential, to ionise some of the gaseous molecules surrounding a pointed conductor which therefore becomes an ion emitter. In the present instance the emitter consists of an array of points in one or more rows (3). The points may be made readily replaceable to allow for erosion. When the drier is operated the fan (4) draws air through the intake (5) and the heater (6) and forces it out through the outlet (7). As it passes the emitter array (3) a proportion of the molecules in the air stream is ionised, and this process exerts a microbicidal effect on the micro-organisms colonising the surfaces of the drier and contained in the incoming air stream. If the ion-producing circuitry is energised for as long as the drier is connected to the electrical supply, decontamination of the internal surfaces of the drier continues even when the drier is not in actual use.

Figure 2 shows an alternative arrangement in which the array of individual emitter points is replaced with a brush of electrically-conductive fibres (8), for instance steel wool, unravelled steel rope, untwisted multi-strand electrical cable or carbon fibres.

Figures 3a and 3b illustrate another alternative arrangement in which the ion emitting element consists of a piece of electrically-conductive foam (9).

Figure 4 illustrates one method of applying the invention to the air intake of a forced-air system by drawing the incoming air through a layer of insulative foam (10) to which is attached a layer of conductive foam (11) connected to the high-voltage generator. This arrangement also performs gross mechanical filtration of the incoming air.

Figure 5 illustrates the application of the invention to the incoming air through a layer of conductive foam (11), the air inside the apparatus by means of an array of pointed emitters (3), the air entering the heating element housing by means of another set of suitablymounted pointed emitters (12) and the outgoing air by means of a further set of suitablymounted pointed emitters (13).

Figure 6 shows the ionisation of a mechanically-propelled air-stream by an emitter or array of emitters (14) inserted in a pipe (15) with or without a nozzle (16) to achieve the microbial decontamination of a surface (17).

Claims

1. A method of killing micro-organisms carried in the airflow of systems in which air is mechanically moved, by means of ionisation.

2. A method of killing micro-organisms resident on surfaces in systems in which air is mechanically moved, by means of ionisation.

3. A method of killing micro-organisms on surfaces by means of a mechanically-propelled stream of ionised gas or mixture of gases.

4. A method as claimed in Claims 1, 2 and 3 in which the ionisation is produced by means of charging a point to a high direct negative voltage relative to earth.

5. A method as claimed in Claims 1, 2 and 3 in which the ionisation is produced by means of charging a point to a high direct positive voltage relative to earth.

6. A method as claimed in Claims 4 and 5 in which the point is replaced by an array of points.

7. A method as claimed in claim 6 in which the array consists of strands of electrically- conductive material.

8. A method as claimed in Claims 4 and 5 in which the point is replaced by electrically- conductive foam.