GB2419533A - Carbon dioxide absorbing clothing device - Google Patents

Abstract

A garment which comprises a CO2 absorbent and a pump. The pump e.g. fan 1 draws exhaled air from the wearer into contact with the absorbent 2. The construction of the garment and the power of the pump 1 are such that the pump 1 is capable of withdrawing air from round the wearer's face at a volume rate at least equal to the exhalation volume rate of the wearer. The device does not use a mouthpiece, nosepiece, hood, or face mask.

Description

ABSORBENT DEVICE

This invention relates to a method and apparatus for absorbing a gas, especially carbon dioxide, from an atmosphere, more especially air.

For an atmosphere in a closed environment to support life it is necessary to ensure the presence of oxygen at a sufficient level for respiration and the maintenance of carbon dioxide below a certain level; physiological problems normally arise sooner from the build-up of carbon dioxide than from the exhaustion of oxygen.

Although numerous appliances have been proposed for absorbing carbon dioxide, these are generally heavy and/or bulky, and are regarded either as fixtures, or as portable only with difficulty. Previously proposed breathing apparatus supplies oxygen and absorbs carbon dioxide in a closed loop, similar to that in a diver's rebreather unit.

Various apparata of this type are disclosed in, for example, GB 2214431, which discloses a closed circuit breathing apparatus providing an antianoxia feature; GB 983,423, which relates to a protective system for isolating a person from a dangerous atmosphere, comprising an enclosing outer garment of material essentially impermeable to the atmosphere and adapted to enclose the person completely therewithin; GB 1463884, which describes a gas and heat protective garment which is a suit made integral with a hood; and DE 10160540, which discloses a double skinned piece of protective clothing for the upper body, including a mouthpiece for transferring exhaled air into a carbon dioxide absorbent.

It is a common feature of all these apparata that there is provided a hood, mouthpiece or similar which either surrounds the head, or transfers exhaled air into the unit.

This impedes the wearer of the apparatus to a greater or lesser extent, and limits his ability to function properly in the relevant environment.

There remains a need for a carbon dioxide-absorption apparatus that is more conveniently portable and more convenient for the user.

The present invention provides a garment which comprises a carbon dioxideabsorbent and a pump, the pump being adapted to draw, in use, exhaled air from a wearer of the garment into contact with said absorbent; characterised in that the construction of the garment and the power of the pump are such that, in use, the pump is capable of withdrawing air from around the wearer's face at a rate at least equal to the exhalation rate of the wearer without a mouthpiece, nosepiece, hood or face-mask being used by the wearer.

It is the purpose of the invention to enable a user to function in an enclosed atmosphere without suffering the build-up of carbon dioxide in that enclosed atmosphere.

Accordingly, an alternative way of regarding the invention is the provision of a garment which comprises a carbon dioxide- absorbent and a pump, the pump adapted to draw, in use, exhaled air from a wearer of the garment into contact with said absorbent; characterised in that the construction of the garment and the power of the pump are such that, in use in an enclosed atmosphere, the pump is capable of withdrawing air from around the wearer's face at a rate such that there is no build-up of carbon dioxide in the atmosphere without a mouthpiece, nosepiece, hood or face-mask being used by the wearer.

The garment may be in the shape of, for example, a vest, shirt, blouse, jersey, sweater or jacket and is preferably sleeveless. It may be put on over the head and/or by using armholes; it may be left unsecured, or closed using, for example, a sliding clasp fastener, buttons, or tapes.

Conveniently, it is shaped like a conventional life jacket, the buoyancy aids being replaced by a carbon dioxide absorbent unit or units.

As carbon dioxide absorbent there may be used, for example, an alkali or alkaline earth hydroxide, or mixtures thereof, if desired or required in admixture with a humectant, e.g., an alkaline earth or magnesium halide, and if desired or required having water incorporated in some way, for example, in the form of water of crystallization.

Examples of suitable materials are molecular sieves, anhydrous lithium hydroxide, and, advantageously, soda lime, a mixture of sodium hydroxide, calcium hydroxide, and water.

A typical formulation of soda lime comprises calcium hydroxide which, measured as calcium oxide, contains 2 to 20% by weight sodium hydroxide and 6 to 20% by weight water, the formulation being capable of absorbing from 25 to 45% of its weight of 002. A preferred formulation comprises, by weight, about 81% calcium hydroxide, 3% sodium hydroxide and 16% water.

The mass of a given carbon dioxide absorbent incorporated in the garment will depend, inter alia, on the absorption capacity of the absorbent, the desired or required breathing rate and the concentration of 002 in the exhaled air from the user for which the garment is designed. For example, 2.5kg of the preferred formulation of soda lime provides sufficient capacity for 24 hour operation by a person breathing at a rate of 12.5 litre/minute who would produce about 24 litre/hour of carbon dioxide under entrapped conditions, which is a typical minimum target specification for an apparatus according to the invention.

The pump withdraws air from around the wearer's face at a rate at least equal to the exhalation rate of the wearer, or at a rate sufficiently great to prevent the build-up of carbon dioxide when the garment is used in an enclosed atmosphere. The power required will depend on the volume of air to be swept away from the vicinity of the wearer's face, the efficiency of the pump and power source combination, and the back pressure imposed by the absorbent. Advantageously, the pump is in the form of a fan, preferably electrically operated. The pump is advantageously one capable of maintaining an air flow in the range 0.5 to 20 m3/h, advantageously 0.5 to 10 m3/h, preferably 1.5 to 6 m3/h, under the load applied by the absorbent unit. A suitable commercially available pump is a DC-powered fan unit sold under the trade name "Megafan" by Papst Motoren GmhH, Series 400F, dimensions 40mm square, about 10mm deep, freeflow rate of 9 m3/h, nominal voltage 5 volts. Such a unit may conveniently be powered by a battery, for example a battery with a high volumetric efficiency, e.g., a power to volume ratio of at least 400 W/litre. Advantageously, the battery has a nominal capacity to weight ratio of 150 Ah/kg.

Suitable batteries include, for example, some high powered alkaline cells and lithium-based cells. Advantageously there is used a lithium-manganese oxide, lithium sulphur dioxide or lithium-thionyl chloride cell or battery of cells, for example those sold under the trade name SAFT, size C, Reference 26500, nominal voltage 3.6v, nominal capacity 7.6 Ah, with a power density of 840 W/litre. The electrical power source, e.g., a cell or cells, may be carried separately or, preferably, incorporated in or otherwise carried by the garment and the invention further provides a garment also having an electrical power source, advantageously one with a power density of 840 W/litre.

A combination of the above-identified fan and 2 cells gives a nominal operational time of between 36 and 50 hours.

The absorbent may be distributed about the garment in any desired manner, the comfort of the wearer and the efficiency of the airflow from the inlet, advantageously near the wearer's face, thiough the absorbent, and to the outlet, being prime considerations. The airflow through the garment may be through the thickness of the absorbent unit or through and around its length. The fan is advantageously placed at the inlet to the absorbent in the vicinity of the wearer's face so that it removes the expired air as close to the face as is practicable without interfering or restricting movement. The fan and battery unit may be an integral part of the garment or may be a separate detachable unit that may be transferred to another panel of the same or a different garment. Alternatively the fan and battery pack may be an integral part of the device with the absorbent material being a separate detachable or replaceable unit. The absorbent may be a fixed or removable panel. The outlet is advantageously placed well away from the inlet to reduce the likelihood of exhaled air short circuiting back to the inlet.

Conveniently, the garment, for example a vest, has front and rear pockets or panels each containing an absorbent unit, the units advantageously being arranged so that air passes through them in series, preferably with the air flow being from the front unit to the back unit.

Alternatively, the garment may be worn initially for half the duration and the absorber blocks at the back and front then exchanged, optionally with or without a detachable fan and battery pack, so that only the front unit is in active use at any given time.

As will be appreciated by those skilled in the art, a chemical absorbent, when in solid form, e.g., a block, granules, or powder, reacts with the incoming medium, the reaction initially being at the absorbent's inlet region. As absorption takes place, the absorbent at the inlet region is exhausted, and a reaction zone travels through the absorbent unit toward the outlet, the size of the zone, and the rate at which it travels, being determined for a given absorbent and gas to be absorbed by the time required for reaction and the flow rate. As the zone reaches the outlet region, breakthrough starts to occur, when there is no longer sufficient time for complete reaction. Accordingly, those skilled in the art may readily provide an appropriate mass of a given absorbent for use for a given purpose.

A garment constructed according to the invention does not require the wearer to use a mouthpiece, nosepiece, hood or face-mask in normal use, and in general such an item will not be provided. Such an item may however be provided with the apparatus if desired, for use in case of battery or fan failure. Activation of the unit may be by any convenient means, for example a tear strip the removal of which allows connexion of the fan motor and battery. If desired, an oxygen source, e.g., an oxygen candle, may be incorporated in the garment.

Two embodiments of fan and absorbent configurations will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a transverse flow configuration and Figure 2 shows an elongate flow configuration.

In each embodiment, a fan 1 draws air from in front of a wearer's face and directs it around and through a block 2 of absorbent. The block 2 has a length 4, a width 6, and a depth 8. In the configuration shown in Figure 1, the air flow is predominantly through the depth 8 of the block. In the Figure 2 configuration, the air flow is predominantly around the block, only some air passing directly through the length 4 of the block, reducing the back pressure on the fan compared with the Figure 1 configuration.

Claims (11)

1. CLk[MS: 1. A garment which comprises a carbon dioxide-absorbent and a

   pump, the pump being adapted to draw, in use, exhaled air from a wearer of the garment into contact with said absorbent; characterjsed in that the construction of the garment and the power of the pump are such that, in use, the pump is capable of withdrawing air from around the wearer's face at a rate at least equal to the exhalation rate of the wearer without a mouthpiece, nosepiece, hood or face-mask being used by the wearer.
2. 2. A garment which comprises a carbon dioxide-absorbent and a pump, the pump being adapted to draw, in use, exhaled air from a wearer of the garment into contact with said absorbent; characterised in that the construction of the garment and the power of the pump are such that, in use in an enclosed atmosphere, the pump is capable of withdrawing air from around the wearer's face at a rate such that there is no build-up of carbon dioxide in the atmosphere without a mouthpiece, nosepiece, hood or face-mask being used by the wearer.
3. 3. A garment as claimed in either claim 1' or claim 2, which is a sleeveless vest.
4. 4. A garment as claimed in any preceding claim, wherein the garment contains at least one pocket or panel containing an absorbent unit.
5. 5. A garment as claimed in any preceding claim, wherein the absorbent is sodalime.
6. 6. A garment as claimed in any preceding claim, wherein the pump is a fan.
7. 7. A garment as claimed in claim 6, wherein the fan has a nominal rating of from 0.5 to 20 m3/h.
8. 8. A garment as claimed in any preceding claim, wherein the fan is drivable by an electrical power source, advantageously carried by the garment.
9. 9. A garment as claimed in claim 8, wherein the power source has a nominal power to volume ratio of at least 400 W/litre.
10. 10. A garment as claimed in claim 8 or claim 9, wherein the power source comprises at least one lithium-based cell.
11. 11. A garment as claimed in any one of claims 6 to 10, wherein the fan and the power source are in a pack, optionally detachable from the garment.