Breath protection mask.

The invention relates to a respiratory mask with filter in the air intake, in particular respirator with an electrically operated ventilation device that draws in ambient air and pushes in the respirator, the filter is disposed in front of the aeration device.

Respirators find z. B. for firefighters or when used in toxic or radioactive aerosols contaminated spaces use. The use of respirators is particularly great in a crisis. Then the respirator cleans the breathing air of biological or chemical warfare agents. Purification is carried out on filter, activated carbon filter found use primarily.

All known filters have a limited operating period. Therefore, the filter must be replaced after a certain operating time. This operating time is selected so that the filter still has sufficient filtering functions at the time of replacement.

The problem is that under the proposed replacement time. In addition, it is uneconomical when the filter is replaced regardless of its load after reaching a certain period of operation. The invention has for its object to carry out a filter replacement only after reaching a certain filter loading, without compromising the user's safety. It is known to measure the loading of gas-protection filters with the aid of a gas sensor, which is arranged behind the filter, wherein the gas sensor is changed in contact with the gas its electric resistance or its voltage or its capacity. The gas sensor is adjusted so that each harmful for the user Gas content is displayed in the flow downstream of the filter immediately. Preferably, the gas sensor occurs already in operation when the harmful gas content approaches the limit of acceptability. See, for example, FR-A-843 542, DE-A-3613512 or GB-A-480 507.

The invention has, in contrast different type, advantageous configurations of gas sensors to content.

In the drawings, various embodiments are shown.

With 1 a ventilation device for a breathing mask not shown is designated. The ventilation device is connected during operation via a flexible lead with the user's head enveloping respirator. The hose connection is designated by 2.

The respirator has a Ansaugstutzten 3. In the drawing of Figure 1, the two nozzles 2 and 3 are closed with screw caps. For connection to the flexible tube, the closures are unscrewed. Further, the closure of the connection piece 3 is unscrewed. There, a filter is mounted. The filter is not shown, for. Example, an activated carbon filter.

The ventilation unit 1 sucks through the filter ambient air. The ambient air is purified in the filter.

The suction takes place by means of a blade wheel 4, which is rotatably mounted in the housing of the ventilation device 1, and is driven by a motor fifth The motor 5 is an electric motor which is powered by a battery with a low voltage current, which is arranged in the part 6 of the ventilation unit 1.

In the aeration device 1, a gas sensor is 7. The gas sensor 7 is connected via a supply line 8 with the cavity in which the Lamellenrad 4 runs.

With the gas sensor electronics 9 is linked.

Figure 2 shows the cooperation of the electronics and sensor in a schematic representation. Referring to Figure 2, the sensor sends a signal to a signal amplification 9. The amplified signal is fed to an analog / digital converter, the output of which appears on a display as required. The display is indicated by 11th In parallel, a limit monitoring 12 is provided. The threshold monitoring 12 is also connected to the signal amplifier 9 and is contact for an optical or acoustic alarm 13, as soon as an allowable value is exceeded. The limit value monitoring 12 can also be used to monitor the battery voltage, which is decisive for the sensor operation.

The gas sensor 7 is designed for the expected gas or the expected gases. Advantageously systems that are particularly sensitive to the predetermined gases. Figure 3 shows a sensor for explosive gases.

Requirement for a gas explosion are flammable gases or vapors, oxygen in sufficient quantity, an ignition source, a particular gas concentration. Combustible gases are very common. These include, for. Example, acetone, acetylene, ethane, ethyl alcohol, ethylene, ammonia, benzene, n-butane, hydrogen cyanide, chlorobenzene, dimethyl ether, 1,4-dioxane, acetic acid, glycerol, carbon monoxide, methane, methylene chloride, naphthalene, nitrobenzene, phenol , Propran, propylene, carbon disulfide, hydrogen sulfide, toluene, vinyl chloride, hydrogen.

Chemical explosions are usually very quickly running oxidations. The required oxygen is present in the ambient air in sufficient quantity. Similarly, there are ignition sources very often. These include burning cigarettes, sparks during switching of electrical contacts, successive striking materials, arcs during welding, etc.

Not any amount of gas causing an explosion. The concentration must have reached a certain minimum value before ignites a gas-air mixture. The sensor of Figure 3 measures the concentration of the gas-air mixture. It works on the principle of "Catalytic combustion" or "heat of reaction". The gas-air mixture passes by diffusion or by means of a gas pump to an active catalyst, heated measuring element. The higher the concentration of the combustible constituents is, the more the sensor, forming the branch of a Wheatstone bridge together with a passive element is heated. The bridge output is proportional to the gas concentration. A measuring amplifier accepts the signals, processes them, directs them as shown in Figure 2 for a display instrument or the interrupt section on.

In Figure 3, the measuring chamber is denoted by 15, the active catalyst 16, the passive with 17. The gas passes through a sintered metal surface of the measuring chamber, passes through a flame retardant wall or flashback barrier 18 and reaches the active catalyst, which reacts in the manner described above.

The gas sensor shown in Figure 3 requires sufficient oxygen for the catalytic combustion. With increasing gas concentration but decreases the oxygen content. The heating of the sensor decreases, the proportionality to the gas concentration is thus called into question. As a result, found the gas sensor of Figure 3 preferably used for determining the lower explosion limit, which is the minimum oxygen content for an explosion. In addition, there is an upper limit of explosion, which denotes the maximum oxygen content at which is given even explosion. Provided that the gas concentration is to be measured over the lower explosion limit, the gas sensor is capable of FIG. 4 The gas sensor according to Figure 4 works according to the principle of the "heat conduit" and is based on that the thermal conductivity of the gases changes with the concentration. Also, the sensor according to Figure 4 is based on a bridge circuit in which a heated platinum wire 20 serves as a measuring and comparison sensor. In Figure 4, the measuring chamber 21, the reference cell is named `` 22nd The platinum wire 20 is formed as a coil and passed through the measuring chamber and the reference chamber. The gas exits as in the gas sensor according to Figure 3 by a correspondingly permeable trained, z. B. sintered metal produced housing wall, through a flashback barrier and reaches the platinum wire 20 where it causes different heating of the applied with the current platinum wire 20.

Gases which are neither flammable nor toxic to humans are dangerous when they contain no oxygen. A transmitter for the oxygen content is shown in FIG. 5 a cathode 26 is made of a large-scale, electron-conducting material between the atmospheric air and a basic electrolyte 25th At its active surface, a reaction plays with the oxygen of the measurement gas. Here, the oxygen to hydroxyl ions degrades. At the same time creates electrical energy. The current which flows between cathode 26 and anode 27, the oxygen concentration is proportional. The reaction of such a cell is extremely fast.

toxic gases of particular danger may be. Frequently occurring gases are, for. Example, acetaldehyde, formic acid, ammonia, arsine, chlorine, chlorine dioxide, hydrogen cyanide, methylene chloride, fluorine, hydrogen fluoride, formaldehyde, carbon monoxide and dioxide, osmium tetroxide, propane, sulfur dioxide, sulfur hexafluoride, hydrogen sulfide, Tetrachlrethan, toluene, chloroform, hydrogen peroxide.

Toxic gases can be measured with semiconductor sensors. The Chemoadsorption plays of metal oxide semiconductors, a role on their surface, causing changes in the conductivity, namely in dependence on the gas concentration.

Figure 6 shows such a gas sensor. The metal-oxide semiconductor is denoted by 30 and held between two electrodes 31 and 32nd The reaction is amplified by means of a heating device, which is formed from a ceramic body and a ceramic body 33 enclosed in the heating coil 34th

Figure 7 shows a gas sensor for the display of carbon monoxide. In essence, the structure of the gas sensor according to Figure 7 corresponds to the gas sensor of Figure 5. However, there is instead of one anode two electrodes, a reference electrode 35 and a counter electrode 36th