GB2305137A - Portable filter for removal of mercury vapours from air - Google Patents

Abstract

A portable air filter apparatus 1 suitable for location on a desk or bench top surface comprises a compact housing 2 having an inlet port and an outlet vent 7, a flexible duct 11 mounted in front of the inlet port, air induction means 6 for drawing ambient air into the apparatus, and a porous treated filter element 10 for removal of air-borne toxins. The filter may be a treated carbon filter for the entrapment of mercury vapours, and the flexible duct 11 may be telescopic.

Description

FILTER This invention relates to a filter and more specifically to an air filter.

Air filters are generally found in areas where it is necessary to ensure that harmful substances present in the air are removed as soon as possible. The most common type of air filter removes dust from the air by drawing the air through a fine mesh filter which traps the dust in the filter and allows the resulting clean air to pass through to be expelled into the atmosphere.

Such a filter is not suitable for extracting harmful vapour substances from the air. In hospitals or dentist surgeries for example, supplies of mercury are kept for use in the production of amalgam fillings for tooth cavities. A leak or spill of mercury in such an environment, and in very small amounts, can result in closure of the surgery while the resulting mercury vapour is removed from the atmosphere. In extreme cases, this can result in evacuation of patients and further risk of infection.

Known air filters are generally mounted on a wall or in a window of a building and cannot be transported to specific locations to deal with spills and leaks of harmful materials at the time of contamination in order to minimise the disruption caused by the incident.

The present invention aims to overcome or at least mitigate the above problems by providing an air filter for use in areas where harmful substances such as mercury are being handled.

According to one aspect of the present invention there is provided a portable air filter apparatus suitable for location on a desk or bench top surface comprising a compact housing having an inlet port and an outlet vent, a flexible duct mounted in front of the inlet port, air induction means for drawing ambient air into the apparatus, and a porous treated filter element for removal of air-borne toxins, the arrangement providing an air-tight gas flow path between the said element and the outlet vents such that all ambient air drawn into the apparatus must pass through the said element before exiting through the outlet vent.

Preferably, the flexible duct is telescopic so that air can be drawn into the filter apparatus from an area remote from the filter.

Preferably also, the porous filter element is a treated carbon filter for removing mercury vapour from air passing through the filter element.

Advantageously, monitoring means may be provided to control the operation of the apparatus and interrogation means may be provided to selectively extract operating information from the monitoring means.

One embodiment of the present invention will now be described with reference to and as shown in the accompanying figure which shows a cross-sectional view of a filter according to one aspect of the present invention. This figure shows a compact, portable filter 1 comprising a generally rectangular housing 2. The housing may be formed of any suitable material such as a plastics material but is envisaged to be formed of a light sheet steel which may be folded into the appropriate shape. A display panel may be provided on the housing on which a plurality of indicating means may be provided.

Such indicating means may include, for example, a time clock and indication means such as a power switch and a warning light. Suitable electronic circuitry (not shown) will be provided for controlling the operation of the indication means.

The front face 3 of the housing is provided with an inlet grill 4 allowing air to pass into the housing. An optional dust filter 5 may be mounted behind the grill to extract dust from the air as it passes into the housing.

A fan 6 is provided within the housing. An extraction grill 7 is provided at the rear of the fan to allow air to be expelled from the filter. The extraction grill may be formed in a rear cover 8 for the housing which is held in position by a plurality of fixing means such as screws (not shown).

Alternatively, the extraction grill may be formed integrally with the housing. The screws pass through apertures in the rear cover into threaded apertures in the rear face of the housing.

A removable cartridge 9 is mounted within the housing 2.

The cartridge contains a treated carbon filter material 10.

The cartridge is of similar cross-sectional dimensions to the housing in order to ensure that all air passing through the filter 1 to the inlet grill 4 to the extraction grill 7 passes through the treated carbon material. The cartridge is located in the housing 2 between runners a and b provided on the base of the housing.

A flexible, telescopic duct 11 is mounted on the front face 3 of the housing over the inlet grill 4. Suitable means may be provided in order to ensure that the inlet grill 4 is completely covered by the end of the duct 11. The free end of the duct 11a is provided with a hygienic filter element 12 which is removably mounted on the free end in order to facilitate removal for cleaning purposes.

A power switch (not shown) may be provided on the rear surface of the housing together with an electrical power supply socket (not shown).

In the event of a spillage of harmful material such as mercury, the filter is placed in an appropriate position for example on a workbench or bench top. The free end lla of the duct is placed adjacent the mercury spill and the filter is switched on. The fan rotates 8 thereby causing air to be drawn through the duct 11, into the housing 2 through the inlet grill 4. The flexible duct 11 can be positioned directly over or in the vicinity of the spillage in order to ensure that the harmful material is removed without delay.

Dust is removed from the drawn air by the dust filter 5, thereby preventing any dust particles from clogging the treated carbon material 10 within the housing and impairing the function of the filter 1. The air within the housing 2 is then drawn through the treated carbon material 10 to remove the mercury vapour within the air and the resulting detoxified air is expelled through the extraction grill 7 at the rear of the housing.

During operation of the filter the time clock on the display panel indicates the length of time which the filter has been operating. It is envisaged that the time clock may be interrogated by a central processor in order to provide information on the efficiency of the filter.

The filter 1 described above is intended to be a portable device which can be placed on a bench top to deal with small harmful spills and leaks in areas such as dentist surgeries and hospital wards.

It will of course be appreciated that the filter 1 can be positioned in a room in an area remote from the source of the harmful material. For example if a dentist is replacing an amalgam filling in a patient's tooth, the amalgam filling has to first be drilled from the tooth. This produces small chips of amalgam and also a detectable amount of mercury vapour.

Such vapour is generally inhaled by the patient during the drilling procedure. With the filter of the present invention, the dentist can position the filter 1 in the room remote from the patient thereby not hampering his or the dental assistant's movements around the patient. The flexible duct 11 can be brought up to a position adjacent the patient's mouth and the filter switched on. Air will then be drawn through the duct 11 from the area surrounding the patient's mouth into the filter and clean air is expelled from the filter back into the room.

It should also be appreciated that the removable filter cartridge allows for simple and efficient replacement of the cartridge without the necessity to empty the treated carbon material from the housing. A replacement cartridge is merely inserted into the housing following removal of the original cartridge which allows the filter to operate on a continuous basis.

The mercury vapour produced during the drilling procedure is drawn into the filter before it is allowed to pollute the atmosphere and the patient is prevented from inhaling a relatively large dose of mercury vapour.

In such an application, the free end of the duct lla may be free-standing and self-supporting or alternatively, a separate stand may be provided to hold the duct in a selected position.

Whilst the filter has been described with particular reference to the extraction of mercury vapour from the atmosphere it is to be understood that the carbon filter material may be treated to retain other harmful substances than mercury. In such cases the operation of the filter will be as described above.

Claims (5)

CLAINS

1 A portable air filter apparatus suitable for location on a desk or bench top surface comprising a compact housing having an inlet port and an outlet vent, a flexible duct mounted in front of the inlet port, air induction means for drawing ambient air into the apparatus, and a porous treated filter element for removal of air-borne toxins, the arrangement providing an air-tight gas flow path between the said element and the outlet vent such that all ambient air drawn into the apparatus must pass through the said element before exiting through the outlet vent.

2 A portable air filter apparatus accordingly to claim 1 wherein, the flexible duct is telescopic so that air can be drawn into the filter apparatus from an area remote from the filter.

3 A portable air filter apparatus according to claim 1 or 2 wherein, the porous filter element is a treated carbon filter for removing mercury vapour from air passing through the filter element.

4 A portable air filter apparatus according to claim 1, 2 or 3 wherein, monitoring means are provided to control the operation of the apparatus.

5. A portable air filter apparatus according to claim 4 wherein, interrogation means are provided to selectively extract operating information from the monitoring means.

6 A portable air filter apparatus substantially as hereinbefore described with reference to and as shown in the drawings.