WO1996019265A1

WO1996019265A1 - Method and equipment to provide air with low level of oxygen

Info

Publication number: WO1996019265A1
Application number: PCT/NO1995/000224
Authority: WO
Inventors: Nils Terje Ottestad
Original assignee: Ottestad Nils T
Priority date: 1994-09-05
Filing date: 1995-12-06
Publication date: 1996-06-27
Also published as: AU4272896A; NO943270D0

Abstract

A method and an installation for supplying breathing air with a lower than normal oxygen content to a closed room (1), in which the pressure is maintained at that of the surrounding atmosphere. In the embodiment of the invention, activities are carried on which, considered in isolation, tend to lower the oxygen content in the closed room to a non-breathable level, while an oxygen control system (14) and a fan unit (7) operating in conjunction with it are used to replace the air in the breathing air in the room with air from the surrounding atmosphere so as to stabilise the oxygen level in the room at a predetermined level. Other gases, especially CO2, which may adversely affect the quality of the breathing air in the room (1), are removed with the aid of a filtering unit (16).

Description

Method and equipment to provide air with low level of oxygen

The invention relates to a method of supplying breathing air with a lower oxygen content than normal breathing air to a basically gas-tight room, in which the pressure is maintained at that of the surrounding atmosphere.

The invention further relates to an installation for supplying breathing air with a lower oxygen content than normal breathing air to a basically gas-tight room, in which the pressure is maintained at that of the surrounding atmosphere.

In activities such as training programmes for athletes, it has been found that practically the same results can be achieved when living and training under normal atmospheric conditions as under altitude conditions, provided that the partial pressure of the oxygen in the surrounding air is the same in each case . Thus, to benefit from the advantages of altitude training without the need to travel to a place located at an altitude, with all the attendant expense, it is advantageous to have the facility of training in an 'altitude room' in which the partial pressure of the oxygen has been reduced to a suitable, desired level.

The only known altitude training facility based on normal atmospheric pressure is a Finnish invention. According to the available information, this concept is based on the continuous circulation of a mixture of oxygen and nitrogen through the room, the supply being controlled so as to maintain the desired oxygen content at all times. In this method, a very high gas flow is required at all times to maintain a uniform gas quality throughout the room and to remove carbon dioxide (CO2) exhaled during the training activities in which the occupants of the room are engaged. It is even more expensive to build an altitude training room in which the air pressure is lowered to a suitable 'high- altitude' level, since this requires an extremely strong wall construction to withstand the normal atmospheric pressure outside. Thus, it has proved difficult to establish the necessary altitude training conditions in a practical and economically acceptable manner.

The purpose of the invention is to provide a method and an installation which, in a simple and inexpensive manner, makes it possible to control the oxygen level in a closed room in which normal air pressure is maintained.

A further purpose of the invention is to provide a method and an installation such that it is unnecessary to supply gases other than ordinary air.

A method of the type described initially has been developed to achieve these purposes. This method is, in accordance with the invention, characterised in that, on the one hand, activities are carried on which, considered in isolation, tend to lower the oxygen content in the closed room to a non-breathable level, and that, on the other hand, the effects of these activities are counterbalanced by replacing the breathing air from the closed room by ordinary air from the outside atmosphere, enabling a predetermined oxygen content to be maintained. To maintain the quality of the breathing air, it is necessary to remove CO2 and other undesirable gases produced by the breathing activities of the occupants of the altitude room. This can be achieved by filtering the air and/or by ensuring that the activities in question require frequent changing of the air in the room.

In principle, the oxygen level may be reduced to the predetermined level by breathing. However, this is likely to be time-consuming in large rooms, even if the level of physical activity is high. It may be desired, especially during initial operation, to perform 'activities' which will reduce the oxygen level in the room rapidly. Catalytic combustion of oxygen may be relevant in this context. Another alternative may be to use a 'nitrogen generator', which will enable considerable quantities of oxygen to removed quickly from the room. Mechanical devices of this type should preferably be based on a special membrane technology which enables air to be separated into an oxygen-rich and a nitrogen-rich component (up to approx. 99% nitrogen). In the preferred method, the nitrogen generator is used to separate air from the altitude room, the nitrogen-rich component being returned to the room and the oxygen-rich component being discharged directly to the surrounding atmosphere. An advantage of this is that the oxygen-rich component will also include any CO2 in the separated air.

Nitrogen generators are commonly used, for example, to establish suitable storage conditions for fruit and vegetables. In this application, the nitrogen generator is adjusted so that the storage room is supplied with air with a constant, low oxygen content. This is achieved by supplying air consisting of the nitrogen-rich component mixed with some of the oxygen- rich component. In this method, therefore, all of the air supplied to the room is supplied by the nitrogen generator.

A nitrogen generator is a relatively energy-intensive device, resulting from the fact that the air pressure must be raised to an estimated 7-10 bar to ensure that the separation process is sufficiently effective. In the method in accordance with the invention, a substantial energy saving relative to the change of air performed in the room is achieved. This is due to the fact that the nitrogen generator is operated only for the purpose of removing oxygen from the altitude room, enabling the oxygen level in the room to be lowered to the desired value at optimum energy consumption. Furthermore, a relatively significant air change can be achieved at moderate energy consumption during normal operation of the room, due to the fact that most of the change is performed by supplying 'fresh' air under pressure directly from the surrounding atmosphere. Thus, it is feasible to perform sufficiently large air changes to eliminate the need for special devices for filtering the breathing air.

The invention is described in further detail below in terms of an embodiment, with reference to a sketch showing a schematic arrangement of an altitude room equipped with an installation in accordance with the invention.

The 'altitude room' 1 shown in the figure is enclosed by impervious walls 2, and by a ceiling and floor, such that the room is effectively gas-tight. The walls incorporate a lock 3 to minimise gas leakage when people enter or leave the room. As shown in the schematic figure, the installation is provided with a first piping system 4, with a number of air intakes 5 in the room 1 and an outlet 6 to remove breathing air from the room with the aid of a fan unit 7 equipped with a fan 8. The installation is further provided with a second piping system 9, with a number of air outlets 10 in the room 1 and an external intake

11 for supplying air to the room from the surrounding atmosphere. The breathing air outlet 6 and the air intake 11 are provided respectively with non¬ return valves 12 and 13, whose purpose is to prevent unintended air leakage into the room.

As shown in the figure, both the air intakes 5 and the air outlets 10 are distributed around the room to achieve a largely uniform air distribution in the room.

The installation further includes an oxygen control system 14 consisting of a number of oxygen sensors which control the fan unit 7 through an electronic control circuit 15, in such manner that the fan 8 is started when the oxygen level falls below a preset value. Although the oxygen sensors are distributed throughout the room 1 , they are represented on the figure by the block 14. The fan 8 is preferably provided with steplessly variable speed control and is arranged to run at increasing speed if the oxygen level continues to fall below the preset value. Thus, the oxygen level is stabilised efficiently by adjusting die supply of air with a normal oxygen content as required to maintain the desired value. The installation also incorporates a filtering unit 16 for removing CO2 and other undesirable gases from the breathing air in the room. The unit consists of a filter housing 17 containing a CO2 absorber 18 and a fan 19, which maintains a continuous flow of a relatively high volume of air through the CO2 absorber. The latter consists of suitable, commercially available material, such as granulated lime. The filtering unit 16 also incorporates a carbon filter to remove the other undesirable gases from the breathing air.

The installation also includes a mechanical unit 20 to remove oxygen from the air in the altitude room. This unit is normally installed outside the room to exclude noise, heat emission etc.

The other climatic conditions in the altitude room can be controlled simply with the aid of suitable, commercially available equipment. For example, condensation in a cooler, in which part of the gas flow through the filter unit

16 is cooled heavily, may be employed to control the air humidity and temperature. If required, the air temperature and relative humidity can be controlled within relatively wide limits by including a dehumidifier using silica gel.

Claims

Patent claims

1. Method of supplying breathing air with a lower than normal oxygen content to a basically gas-tight room, the pressure in the closed room being maintained at mat of the surrounding atmosphere, CHARACTERISED IN

THAT, on the one hand, activities are carried on which, considered in isolation, tend to lower the oxygen content in the closed room to a non- breathable level and that, on the other hand, the effects of these activities are counterbalanced by replacing the breathing air from the closed room by ordinary air from the outside atmosphere, enabling the oxygen content to be maintained at a lower level than in normal air while maintaining the quality of the breathing air by removing gases produced in the closed room by filtering as required.

2. Method in accordance with patent claim 1 , CHARACTERISED IN THAT a relevant activity is to utilise the consumption of oxygen caused by the breathing activity of the occupants of the room, preferably while these are engaged in hard physical activity.

3. Method in accordance with patent claim 1 , CHARACTERISED IN THAT a relevant activity is to remove oxygen from the air in the room by means of mechanical devices or, alternatively, by supplying the room with air which is highly rich in nitrogen.

4. Method in accordance with patent claim 1, CHARACTERISED IN THAT the method in accordance with patent claim 3 is used during an initial operating period, following which the method in accordance with patent claim 2 is used.

5. Installation in accordance with patent claim 4, CHARACTERISED IN THAT it incorporates a mechanical device (20), preferably a nitrogen generator, to remove oxygen from the air in the closed room.

6. Installation in accordance with patent claim 4 or 5, CHARACTERISED IN THAT the speed of the fan (8) in the fan unit (7) is steplessly variable, and that it (the fan) is arranged to run at increasing speed as the oxygen level in the room continues to fall below the preset value.

7. Installation in accordance with patent claim 4, 5 or 6, CHARACTERISED IN THAT the breathing air outlet (6) and the external air intake (11) are provided respectively with non-return valves (12 and 13).

8. Installation in accordance with any of patent claims 4-7,

CHARACTERISED IN THAT the breathing air intakes (5) and the air outlets (10) are distributed around the room (1) so as to achieve a generally uniform quality of breathing air everywhere therein.

9. Installation in accordance with any of patent claims 4-8, CHARACTERISED IN THAT the filtering unit (16) is provided with a fan

(19) capable of supplying a continuous flow of air of a relatively high volume through the unit.

10. Installation in accordance with patent claim 9, CHARACTERISED IN THAT the filtering unit (16) incorporates a CO2 absorber (18) for removing carbon dioxide, and that a carbon filter for removing other undesirable gases from the breathing air in the room (1) is also installed.