A METHOD AND A SYSTEM FOR DISINFECTING AIR IN AIR CONDITIONING DUCTS

Abstract: A method for disinfecting air in ventilation ducts, on which a non-poisonous and substantially non-volatile disinfectant, in particular a quaternary ammonium complex, is vaporised as an aerosol by means of micro vaporisers into the air flow in the duct, and is allowed to precipitate on the walls of the duct, and in which, furthermore, the air in the duct can be ionised without substantial ozone production, as well as a system for executing this method, comprising an air duct portion (1) with means for disinfecting the air flow (2) therein, comprising an assembly of vaporising nozzles (5) connected, by means of a metering pump (10), to a reservoir (11) for dissolved disinfectant, and a flow meter (3) for controlling the metering pump (10), and, moreover, ionisation electrodes (4) can be provided in the duct (1) which are connected to a high-voltage source, and, at some distance down-flow of these electrodes (4) an ozone sensor (6) is arranged which is connected to control means (8) adapted to control the high-voltage source.

Description: A metho d an d a system for -disinfecting air in air conditioning ducts. When, in closed spaces, air is supplied by means of air supply and/or conditioning ducts, it is to be avoided that irritating or harmful germs, in particular fungi, algae, microbes, viruses and the like, will be introduced into the 5 space since they can harm the health or at least the comfort of persons present therein. An objection of air filters is that they will generally procure an incomplete removal of such germs, so that the germs let through can develop further, and, when improving 10 the filtering efficiency, the pressure drop over such filters will increase accordingly. In the case of moist and warm air very favourable conditions for the growth of such germs can occur. A good air disinfection is especially important when a 15 substantial part of the air introduced into the closed space is recycled, as, for instance, in aeroplanes. Eliminating germs by means of poisonous substances is not allowed in most countries, if these substances can reach the space in which persons are present. 20 The invention provides a method for the above-mentioned purpose, which does not have these objections, which method is defined in claims 1..5. The non-poisonous disinfectant kills fungi, algae and similar organisms, and is active not only in the air flow 25 itself, but, by precipitation thereof on the walls of the duct, also in a prolonged way on the germs precipitating thereon which may return again in the airflow later, so that also these germs can be effectively suppressed. When, moreover, the air is ionised, not only microbes and viruses / ~ 30 will be effectively suppressed, but also the vapourised disinfectant particles will be charged, so that they will deposit faster on the duct walls. When the air flowing through the duct is to be moistened, preferably the same disinfectant is added to the water used therefor, in order to counteract thereby the introduction of harmful germs into the duct. The system for executing this method is defined in claims 6 and 7. The invention will be elucidated below in more detail by reference to a diagrammatic drawing of a non-limiting embodiment of a system according to the invention. The system shown in the drawing comprises a part of an air ventilation duct 1, the air flow flowing therein being indicated by arrows 2. In the duct 1, as seen in the flow sense, are consecuti¬ vely arranged a flow sensor 3, an assembly 4 of particularly needle-shaped air ionisation electrodes, an assembly 5 of disinfectant vaporisers, and an ozone sensor 6. These elements are connected, by means of electric leads 7, with a control apparatus 8 which also comprises a high- voltage source for the electrodes 4, the vaporisers 5 being connected, by means of a tube 9, with a pump 10 which can pump the disinfectant dissolved in water from a reservoir 11. The flow sensor 3 is adapted to disconnect the pump 10, and, if required, also the electrodes 4, if the air flow 2 decreases below a given threshold value, and it is also possible to adapt the operation of the pump 10 to the air flow rate. The ozone sensor 6 is adapted to lower the voltage at the electrodes 4 if an ozone content threshold is exceeded. This voltage should, generally, be lower than 10 kV. In this manner >10 12 l.ons/s can be produced at a current intensity of some μA. The air ionisation, in particular when producing negative ions, will cause microbes, viruses and similar micro-organisms present in -the air flow to be annihilated. A very important effect of this ionisation is, furthermore, that the disinfectant particles are being charged too. Thereby these particles will be driven towards the duct walls, which, as indicated at 12, are grounded, so that these particles will deposit on the walls, ∑f, now, fungi, algae or the like also deposit on the walls, they will be killed, or at least their growth will be inhibited, by the continued contact with the disinfectant in such a degree that no dangerous growth thereof will occur. Since the air flow in the duct 1 will, eventually, reach the working or living space, the disinfectant should comply with the most severe requirements imposed by public health services. Therefore it definitely should not contain mercury, formaldehyde, phenol or the like, and, because of fire hazard, in particular in the case of ionisation, the use of alcohol is not allowed either. The disinfectant used according to the invention is a quaternary ammonium compound, commercially available under the name "Dessair 2000", and being approved by the Swiss inspection service as being non-poisonous ("Giftklasse Frei" BAG T 73512 DC). This disinfectant consists of a quaternary ammonium complex, in particular a benzyl ammonium chloride, such as n-octyldimethyl, 1,1,3,3-tetrabutyl phenoxy ethyldimethyl or 1,1,3,3-tetrabutyl-o-ethoxydimethyl benzyl ammonium chloride. The invention is, however, not restricted to these examples. This disinfectant is sold in concentrated form (16 % active substance), and the concentrate will, for example, be added to the water in the reservoir 11 in a ratio of 1:100. Preferably demineralised water is used therefor. The mist particles formed by the vaporisers 5 having, for example, a mean size of about 50 μm, precipitate on the walls of the duct, in particular because they obtain a charge by the ionisation of the air, causing them to be attracted towards the duct walls, and then the water can evaporate for the greater part. Some decomposition may take place, which, however, will not lead to noxious products. This disinfectant is, moreover, active against (in particular disagreeable) smells. When air moistening is required, water can be vaporised in a suitable point of the duct 1 and under control of the control apparatus 8, and, as a matter of fact, a humidity sensor can be used then. Preferably the same disinfectant is added to the water used therefor so as to counteract the introduction of fungi, algae and the like. The system can, for instance, comprise a microprocessor, and can be connected to remote indicating and/or adjusting means allowing remote control or measurement.

Claims: C L A I M S 1. A method for disinfecting air in ventilation ducts, characterised in that a non-poisonous and substantially non¬ volatile disinfectant in water is vaporised as an aerosol by means of micro-vaporisers into the air flow in the duct, and is allowed to precipitate on the walls of the duct. 2. The method of claim 1, characterised in that the disinfectant is a quaternary ammonium complex, in particular a benzyl ammonium chloride. 3. The method of claim 2, characterised in that the disinfectant is dissolved in an amount of about 0,16 % in 3 water, an amount of about 0,06..0,08 ml/m being vaporised in the air at an over-pressure of about 0,35 MPa at an average vapour particle size of about 50 μm. 4. The method of any one of claims 1..3, characterised in that the air in the duct is ionised without a substantial ozone production. 5. The method of any one Of claims 1..4, characterised in that the disinfectant is added to water to be used for air moistening. 6. A system for executing the method of any one of claims 1..5, comprising an air duct portion (l.) with means for disinfecting the air flow (2) therein, characterised by an assembly of vaporising nozzles (5) connected, by means of a metering pump (10), to a reservoir (11) for dissolved disinfectant, and by a flow meter (3) connected with a control means (8) and adapted to disconnect the metering pump (10) by means of the control means (8) as soon as the air flow (2) decreases below a given boundary value, and, if required, to regulate the operation of the metering pump (10) in function of the air flow (2). 7. The system of claim 6, characterised in tha , in the duct (1) , are provided particularly needle-shaped ionisation electrodes (4) adapted to ionise the air (2) flowing through the duct (1) , which electrodes (4) are connected to a high- voltage source, and in that at some distance down-flow of these electrodes (4) an ozone sensor (6) is arranged which is connected to control means (8) adapted to control the high-voltage source in such a manner that substantially no ozone is produced in the air (2) .

Inventors: WEIBEL RENE, WEIBEL, RENE
Applicants: DESOSTAR HOLLAND BVIO, LIWIHOLD BV, WEIBEL RENE, DESO STAR HOLLAND B.V. (I.O.), LIWIHOLD B.V., WEIBEL, RENE
Application year: 1993
Main classification: F24F3
IPC codes: F24F3