WO2003068273A1

WO2003068273A1 - Air disinfection unit

Info

Publication number: WO2003068273A1
Application number: PCT/DK2003/000097
Authority: WO
Inventors: Henrik Hendriksen
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-02-14
Filing date: 2003-02-14
Publication date: 2003-08-21
Anticipated expiration: 2004-08-14
Also published as: AU2003208300A1

Abstract

An air disinfection unit comprising a prefilter, a ventilator, a HEPA filter and a UV-C light source is disclosed. The unit is especially useful for disinfection, purification in hospital areas, operation rooms, laboratories, areas where people with allergies are treated, clean room separation areas, air distribution system, air sluices, areas where food items and the like are packed, inside fresh food packaging or display machines, etc.

Description

Air Disinfection Unit

The present invention relates to an air disinfection unit for disinfecting and filtering air in which unit air is passed through a housing from an air inlet opening to an air outlet opening at a selectable air flow rate, where a ventilator is provided inside the housing, said ventilator providing the air flow.

This kind of air disinfection unit can be used in an number of places where filtering and disinfection of the air is desirable. As examples can be mentioned hospital areas, operation rooms, laboratories, areas where people with allergies are treated, clean room separation areas, air distribution systems, air sluices, areas where food items and the like are packed, inside fresh food packaging or display machines, etc.

In all these places there is a need to avoid or minimise the presence of bacteria, vira, dust, fungus, smoke etc. For this purpose a number of air condition units have been presented which to a certain degree manages to keep dust out of the air or kill off certain types of vira or bacteria. One such air disinfection unit is known from US 5505904 where an air disinfection unit is disclosed in which air is passed though a housing from an air inlet to an air outlet opening at a predetermined air flow rate under substantially uniform cross-sectional air flow conditions. Inside the housing is, fur- thermore, located a number of UV-C irradiation lamps. The air flow in the housing is controlled such that the air borne bacteria will remain in the enclosure for a certain amount of time, i.e. sufficient time for the UV-C light rays to destroy the bacteria.

However, in order for this system to work it is necessary to create a uniform air flow across the UV-C light source and, furthermore, to control the air flow such that the bacteria remains at close vicinity to the light sources for a certain period of time in order for the light rays to have sufficient time to destroy the bacteria.

In order to achieve this limited air flow around the light bulbs this consequently limits the amount of air which can be pushed through the disinfection unit. In order to in- crease the air flow rate, it will be necessary to install more light sources, which again will increase the cost dramatically.

Furthermore, as the effectiveness of the device is relying completely on controlling the presence of the bacteria in the vicinity of the light bulbs for a certain amount of time this can cause huge variations in the effectiveness of the device as this air flow is determined by a number of parameters, among others the air pressure in the surroundings, sudden changes in air pressure as well as temperature differences in the surroundings.

There is, therefore, a need for an air resistant disinfection unit which constantly, without depending on the surrounding environment, assures an extremely high degree of disinfection. Furthermore, the destruction of bacteria, vira and other micro organism must be performed reliably and at variable air flow rates.

It is, therefore, an object of the present invention to provide an air disinfection unit which overcomes the problems listed above.

The invention solves this problem by providing an air disinfection unit which is par- ticular in that a further filter of the HEPA type is provided adjacent to the light source and that the light is a UV-C light source. Extensive research has shown that UV-C light, and especially around the 254 nm wavelength, is extremely effective in destroying the genetic makeup of bacteria, vira and other micro organisms. By being able to consistently and reliably expose the micro organism, bacteria and vira to UV-C light rays a very high disinfection efficiency can be attained.

The known disinfection devices using UV-C light sources attain a rather low watt effect on the exposure of the micro organism. For example, the traditional UV-C light bulbs/tubes with a 40 W effect effectively have 10 or 11 W used due to the installation in a moving air stream. By selecting especially effective UV-C light tubes where the glass is made from quarts and not placing the tubes in a turbulent air flow, a higher effective exposure, for example up to 20 W effective can be attained. Furthermore, by arranging a HEP A filter adjacent the light source the bacteria, vira and other micro organioms get caught in the filter material. As the UV-C light source is arranged in the immediate vicinity of the HEPA filter the bacteria, vira or micro organism will be exposed far more reliably and consistently in comparison to what is known from the prior art. Even those bacteria, vira or micro organisms which are smaller than the mesh size of the filter unit will be sufficiently delayed during the passage of the filter material in order for the UV-C light rays to be able to destroy the organism. Consequently, a much improved performance and a consistent high efficiency of the air filtering unit is attained regardless of the air flow rate through the filtering unit.

In a further advantageous embodiment the HEPA type filter is of class EU 13 or higher, equivalent to at least a filtering efficiency of 99,997 % at 0,3 nm particle size. The filter class EU 13 is in accordance with the European standards for classification of filters. Class 13 filters or higher, the highest class being 17, is used in clean rooms and in nuclear installations, where an extreme air purity is desired. In hospitals and especially in environments where surgery is performed the norm is EU 12 filter quality. In the food packaging and food processing industry EU 9 filters are used.

By using filters of class 13 or higher it is assured that the micro organisms, bacteria or vira will be either caught or sufficiently delayed through the filter material, so that an efficient exposure through the radiation from the UV-C light source is attained, whereby, even at higher air flow rates, an efficient disinfection will be achieved.

The construction according to the invention where the UV-C light source is arranged immediately adjacent to the filter unit assures an extremely advantageous disinfection process with simple means.

In a further preferred embodiment the UV-C light source is a 40 W or more low pres- sure quarts tube which produces UV-C irradiation at a wave length of about 254 nm with an intensity of at least 120 μ W/cm². As explained above, especially UV-C radiation with a wave length of about 254 nm has a devastating effect on the genetic structure of the micro organisms that are caught in the filter. By using a light source as mentioned above it is assured that the effective wattage to which the micro organisms are exposed remains high regardless of the air flow in the unit. The success rate of destruction is also coupled to the intensity of the light at the exposure zone.

In a still further inventive embodiment of the invention the ventilator with prefilter in its intake opening, the HEPA filter and the UV-C light source including appropriate electrical supply equipment is arranged inside a housing, where the prefilter is part of the housing surface and that only control means for controlling the fan speed of the ventilator, switching means and an electrical connecting cord is available for interface with the unit on the surface of the housing.

By assembling all the elements in a housing the unit becomes easy to use and operate in that the user only has to switch the unit on and select the appropriate fan speed on the control means after having plugged the unit into the available means of electrical supply. Furthermore, by designing the housing a pleasant appearance can be achieved, whereby the air disinfection unit in contrast to prior art devices can fit nicely into the environment where they are desired to operate.

In order to further improve the usability and user friendliness of the unit the housing can be mounted on wheels, whereby it becomes easy to move the unit around or store it when not in use.

In a further advantageous embodiment tests have shown that ventilators having a capacity of 150-800 m³/hour, more preferably 200-700 m³/hour and most preferred 300- 500 m³ hour, provides sufficient flow rates through the unit, whereby the unit is suitable for most applications and room sizes. The ventilator's through put of air is deci- sive on the effectiveness in the prior art applications, but due to the arrangement of the HEPA filter directly adjacent to the UV-C light source the air flow as such does not have an overwhelming influence on the effectiveness of the disinfection unit. In order to keep track of the use of the unit an hour counter can be mounted, preferably such that the number of hours during which the unit has been in use can be read from the outside. The number of use hours is decisive for determining when the filters, both the prefilter and the main HEPA filter, need to be cleaned or replaced. Typically, the unit can run for approximately 6000 hours before it is necessary to replace the

HEPA filter and the UV-C tubes. Depending on the environment in which the unit is placed, the prefilter, which in a further advantageous embodiment is a EU class 3 filter, needs to the cleaned at shorter intervals.

In a further advantageous embodiment of the invention the HEPA filter has a surface of 6-20 m², preferable 8-15 m² and most preferred 10-12 m². The physical size of the filter in combination with the filter classification determines how much resistance the filter unit offers to the air flow. Tests have shown that filters in the range stated above consistently provide a steady air flow for the approximately life time of the filter, whereby the intended efficiency of disinfection of the unit will reliably be attained.

In yet another preferred embodiment the HEPA filter is in the shape of a filter cartridge wherein the filter material is pleated, said filter cartridge having a cylindrical configuration and that the ventilators outlet is arranged at one end of the cylindrical filter cartridge and a mounting for the UV-C light source is arranged in the opposite end such that the light source, for example in the shape of a tube, is arranged inside the cylindrical configuration of the filter cartridge.

In this configuration the air to be filtered is sucked into the unit by the ventilator. It is then blown down into a cylindrical hollow, limited by the pleated filter cartridge and a mounting in the opposite end of the filter cartridge for the UV-C light source. As stated above it is preferred to utilise a tube shaped light source as this will emit light to a large area and especially in this embodiment will expose substantially the entire interior surface of the filter. The air blown down into the filter cartridge will be evacuated through the filter wall. The housing of the unit will therefore have perforations, netting or other means for letting the air out in the vicinity and corresponding to the cylindrical shape and size of the filter cartridge. The invention will be explained with reference to the enclosed drawing. Although the following explanation relates to a specific example, it should be understood that the invention is not limited to this specific example, but can have other practical designs or layouts within the definition of the claims and the description as such.

Fig. 1 illustrates one example of the unit according to the invention. Fig. 2 illustrates a typical cross-section of a unit according to the invention. Fig. 3 illustrates a preferred embodiment of the invention. Fig. 4 illustrates a preferred embodiment of the invention.

The unit 1 illustrated in fig. 1 illustrates one embodiment of the invention. In this embodiment the unit 1 consists of a housing 2, mounted on wheels 3 such that the unit easily can be rolled across the floor. In this example the unit is shown as a circular unit being approximately 1 metres high and having a diameter of about 40 cm. In this con- nection it should be mentioned that the unit can have any desired cross-sectional shape, for example rectangular, quadratic, triangular or any polygonal shape desired. The exterior dimensions of the unit as such are determined by the physical size of the ventilator inside the unit as well as the desired filter size.

On the outside of the unit a control panel 4, an hour counter 5 and a connecting cord 6 for connecting the unit 1 to the main supply are provided.

On the control panel there is in this example illustrated two manipulators, the on/off switch 7 and the fan speed control 8.

The top of the cylinder is the air inlet opening 9 where the prefilter is mounted. The air outlet opening is at the opposite end of the cylinder.

Turning now to fig. 2 a cross-section of the unit 1 as illustrated in fig. 1 is shown. The same features in fig. 1 are denoted with the same reference numbers corresponding to fig. 1. In this example a prefilter 10 is arranged in the air inlet opening 9 whereby dust and other larger particles can be filtered before the air to be disinfected enters the disinfection sector of the unit 1. Typically, the prefilter 10 will be a filter of class EU 3 as the air flow resistance in such a filter is low in relation to its ability to withhold dust and other larger particles. The ventilator 11 creates the air flow through the unit and is controlled by the control panel 4. From the ventilator 11 the air flow is directed towards the HEPA filter 12. In this example the HEPA filter is a class 13 filter with a pleated structure so that the entire filtering surface of the filter is in excess of 10 m². Filters of this type can be obtained from "American Air Filters" or similar suppliers.

Immediately below the HEPA filter 12 the UV-C light source 13 is arranged. The UV- C light source emits UV-C irradiation at 254 nm at 40W. As the filter and the UV-C light source are arranged in immediate vicinity of each other the radiation will effectively hit all bacteria, vira or micro organisms caught in the filter unit. The disinfected air will thereafter leave the unit through the air outlet opening at the bottom of the housing 2. At the bottom of the housing is also arranged a storage compartment 14 for the electrical cable 6 connecting the unit to the main supply. Advantageously, a roll up mechanism can be arranged inside the cable compartment 14, whereby the cable 6 can be rolled up inside the unit when not in use.

In fig. 4 a unit according to a preferred embodiment is shown. The same unit is illustrated in fig. 3 in a cut away view where the UV-C light source 13 can be seen mounted on the bottom plate 14 of the unit. The filter unit 12 is in this example a cylindrical cartridge having a pleated structure. The filter cartridge is arranged so as to surround the UV-C light source 13. The unit's prefilter, ventilator and control panel is not shown in fig. 3 as fig. 3 only aims to illustrate the arrangement of the HEPA filter cartridge 12 in relation to the UV-C light source 13.

As illustrated in fig. 3 the UV-C light source 14 is mounted in the bottom plate 16 of the unit. For replacement or cleaning of the UV-C light source 13 the light source 13 can be removed from the bottom 16 by removing the light source 13 with the fastening means 15. The unit in fig. 4 has an interior where the upper half corresponds to fig. 2 and the bottom half corresponds to fig. 3. The air is let in through the prefilter 9 and behind the housing 2 the installations relating to the ventilator, prefilter, control panels etc. are arranged. The bottom section 17 of the housing is in this embodiment perforated or is a netting structure. This is done in order to let the air out again from the filtering unit. By using a filter cartridge 12 with a pleated surface of about 10 m² and a ventilator which creates an air flow rate through the filter unit of approximately 3-500 m³ per hour, a very effective disinfection and filtering can be achieved and at the same time the air velocity through the filter and the perforated or netting section 17 of the unit can be kept relatively low.

The unit 1 and in particular the prefilter 10, the HEPA filter 12 and the light source 13, are made such that all parts can easily be dismantled when cleaning, replacing og repairing. This is an added and important feature in that this type of unit is often placed in environments where an extremely high hygienic standard is desired.

Claims

1. Air disinfection unit for disinfecting and filtering air in which unit air is passed through a housing from an air inlet opening to an air outlet opening at a selectable air flow rate; a ventilator is provided inside the housing and a prefilter is arranged adjacent to the ventilators' air intake opening and an ultraviolet light source is provided in the housing, characterised in that a further filter of the HEPA type is provided adjacent to the light source and that the light is a UV-C light source.

2. Unit according to claim 1, characterised in that a prefilter is arranged in the ventilators' intake opening.

3. Unit according to claim 1 or claim 2, characterised in that the HEPA type filter is of class EU 13 or higher, equivalent to at least a filtering efficiency of 99.997 % at 0,3 nm particle size.

4. Unit according to claim 1 or claim 3, characterised in that the UV-C light source is a 40 W or more, low pressure quarts tube which produces UV-C irradiation at a wave length of about 254 nm with an intensity of at least 120 μ W/cm².

5. Unit according to any of the proceeding claims, characterised in that the ventilator with a prefilter in the intake opening, the HEPA filter and the UV-C light source including appropriate electrical supply equipment are arranged inside a housing where the prefilter is part of the housing surface and that only control means for con- trolling the fan speed of the ventilator, switching means and an electric connection cord is available for interface with the unit on the surface of the housing.

6. Unit according to claim 5, characterised in that the housing is mounted on wheels.

7. Unit according to any of the proceeding claims, characterised in that the ventilator has a capacity of 150-800 Vhour, more preferably 200-700 m³/hour and most preferred 300-500 m³/hour and that the ventilator optionally is supplied with an hour counter.

8. Unit according to any of the proceeding claims, characterised in that the prefilter is a EU class 3 filter.

9. Unit according to any of the proceeding claims, characterised in that the HEPA filter has a surface of 6-20 m², preferably 8-15 m² and most preferred 10-12 m².

10. Unit according to any of the proceeding claims, characterised in that the HEPA filter is in the shape of a filter cartridge wherein the filter material is pleated, said filter cartridge having a cylindrical configuration and that the ventilators outlet is arranged at one end of the cylindrical filter cartridge and a mounting for the UV-C light source is arranged in the opposite end such that the light source, for example in the shape of a tube, is arranged inside the cylindrical configuration of the filter cartridge.