The apparatus is intended to ventilate the room according to the air condition in the room, and to that end uses a combination of air quality monitoring and control means, responsive to the air quality, for controlling an air extractor and, optionally, an air intake for the room. The atmosphere inside and outside the room, referred to herein as air whatever its specific composition, is moved by air propulsion means, which may be any suitable fan or impeller, such as a positive pressure fan. If air is extracted and taken in simultaneously, air heat recovery may be used between the two air streams.

It is one object of the invention to utilise a sensor for a specific air constituent or group of air constituents in order to control ventilation. The ventilation requirements differ according to the nature of the constituent and its quantity.

Examples of air contaminants that require different responses are water (air moisture content or humidity), smoke, carbon monoxide, and radon. Other air constituents, while not being contaminants, may also give rise to adverse air quality ; for example, oxygen depletion should also initiate ventilation.

Unacceptable atmospheric levels of each of the foregoing require a specific ventilation response in addition to an alarm output as may be required.

Furthermore, a sensor appropriate for one air constituent will not necessarily be appropriate for making useful measurements of the levels of different constituents. Appropriate sensor means for different constituents are known in the art.

There are many possible variables iin the configuration of ventilation apparatus

and its sensor and control systems for ventilating a room. An arrangement that is economical or convenient to instal may well not give accurate or sensitive air condition monitoring. For example, the inclusion of sensors within the actual ventilation ducts for extracting air, while ensuring a good flow of air over the sensor while the extractor is operating, will allow the sensor to be influenced by external air when no ventilation is taking place, limits the circulation of room air past the sensor at that time, and may cause excessive build up of airborne dust particles on the sensor surfaces. Location of the sensors elsewhere in the room means that monitoring is closely dependent on the natural room air circulation past the sensors.

According to the present invention, there is provided a ventilation apparatus for ventilating a room according to air condition in the room, comprising a relatively high throughput air extractor or intake duct and associated air propulsion means, a relatively low throughput air sampling duct and associated air propulsion means, sensor means in the air sampling duct responsive to changes in air quality, and control means for controlling the air propulsion means associated with the air extractor or intake duct, the sensor means being operatively connected to the control means to provide thereto data indicative of air quality, and the control means being operatively connected to the controlled air propulsion means to control the same in response to said air quality data.

The high volume air extractor or intake duct with their associated air propulsion means, or both of them, provide the primary means of ventilating the room, while the low volume sampling duct contains the sensor or sensors which may be provided with a modest air flow just sufficient to maintain effective monitoring, although greater sampling flow rates are of course possible. The air propulsion means associated with the sampling duct may operate over an extended period, during which the sensor means are activated substantially continuously, irrespective of the room ventilation being carried out by the high volume duct or ducts. Essentially, air quality can be monitored continuously while the ventilation apparatus is operating. However, if circumstances demand,

the air propulsion means associated with the air sampling duct may operate intermittently, in which case the sensor means may be activated only while the air propulsion means are operating.

Placing the sensor means in a sampling duct with associated air propulsion means allows the sensors to be exposed to a moving three dimensional plume of air, taken from the room volume, rather than being exposed only to relatively static air over the sensor head or heads.

The sensor means are desirably responsive to changes in air quality due to each one of a plurality of constituents. These may include particle constituents, such as in smoke ; toxic constituents, such as carbon monoxide ; radioactive constituents, such as radon ; constituents which adversely affect human comfort or the physical condition of materials in the room, such as water vapour, and in which category high or low temperatures could be included ; and constituents which are detrimental by virtue of being inadequately present, such as oxygen.

The sensor means may be operatively connected to the control means in a manner whereby to discriminate between air quality data related to one constituent and air quality data relating to another constituent. Suitably, the sensor means are operatively connected to the control means by a distinct channel for air quality data relating to each discriminated constituent.

The control means may comprise means for receiving air quality data from the sensor means, means for evaluating the received data, and means for supplying start and stop signals to the controlled air propulsion means according to the values of the received data. A microprocessor provided with suitable input and output stages may perform these functions. The control means are preferably adapted to resolve conflicts in the supplying of start and stop signals which might arise from conflicting responses relating to different constituents simultaneously. For example, detection of smoke, indicative of a fire, might normally trigger ventilation by air extraction from the room, while detection of

carbon monoxide might normally trigger ventilation by drawing extemal air into the room. However, in the event of a fire, positive ventilation with oxygen-laden air could be disastrous. Accordingly, the control means may be adapted to resolve such conflicts by giving an order of precedence to the responses to data relating to the different constituents. If the plurality of constituents to which the sensor means are responsive include a constituent indicative of fire and at least one of a toxic constituent, a radioactive constituent and water, the control means may be adapted to give precedence to the responses to air quality data values derived from a constituent indicative of fire, and the lowest precedence to the responses to air quality data values derived from water.

In an especially preferred embodiment, all the said ducts and air propulsion means, sensor means and control means are contained within a single housing.

Thus, the invention can provide a dynamic system within a single ventilator housing that can continuously monitor air condition and respond in a prioritised manner dependent on the type and level of contamination. The housing is typically located in a building, each duct extending between the said room and extemal atmosphere. When the apparatus includes both a relatively high throughput air intake duct and a relatively high volume throughput air extractor duct, they may be connected by heat exchanger means whereby to reduce any temperature differential between air propelled through the two ducts, and recover heat accordingly, in a manner known in principle in the art.

One embodiment of the invention, suitable for use as a ventilation monitoring and control apparatus within domestic kitchens and bathrooms, is illustrated, by way of example, in the accompanying drawings, in which: Figure 1 is a perspective view of a housing forming part of and containing all the remainder of ventilation apparatus, as it might be mounted within a room on the inner face of an exterior wall of a building, the housing being illustrated transparently in order to show its contents;

Figure 2 is a diagram of the control means and its relevant associated inputs and outputs; and Figure 3 is a table showing the priority ratings and responses set by the control system for a range of conditions detected by the sensor means.

Figure 1 shows the physical arrangement of the elements of the apparatus. A rectangular housing 10 contains a relatively large diameter air extractor duct 12, a similar diameter air intake duct 14, and a relatively small diameter air sampling duct 16, each extending between the front wall 18 of the housing, where the respective ducts are covered by grilles 22,24,26 and open into the room, and the rear wall 20 of the housing, where the respective ducts extend through the room wall on which the housing hangs and open to the extemal atmosphere outside the room.

The extractor duct 12 and the intake duct 14 contain respectively an extractor fan 32 and an intake fan 34 for propelling air through the respective ducts when activated. The extractor fan propels air from the room to the extemal atmosphere, while the intake fan propels air from the extemal atmosphere into the room. Typical extraction and intake air flow rates are around 100m3/hr.

More precisely, rates from 54m3/hr to 220m3/hr may be appropriate, depending on kitchen or bathroom requirements. Not shown in the drawings, conventional heat exchanger means may be used between the two large diameter ducts in order to recover heat from air in one duct and transfer it to air in the other duct.

This can be applied to heat conservation in the room, or to any heating or cooling purpose that may be appropriate.

The sampling duct 16 contains a fan 36 for propelling air from the room to the exterior atmosphere. Room air entering the sampling duct through its inlet grille 26 is drawn next through a dust filter 28 and then through a sensor array 30 before being drawn into the fan 36 at a rate of around 1 m3/hr, giving a sampling flow rate of about 1 % of the intake or extraction flow rate. The sensor array

contains a plurality of senso means for detecting humidity, radon, carbon monoxide and smoke, according to known principles in the art.

Continuous sampling or intermittent sampling may be used. In the latter case, operation for 5 seconds every 50 seconds would reduce the sampling power requirement by 90%, suitable for a solar powered system.

The fans in each of the three ducts are conventional axial fans with two consecutive sets of blades. Any other suitable air propulsion system could be used instead.

On the rear wall 20 of the housing is mounted control means 38, connected to the sensor means by a plurality of sensor cables (not shown). The purpose of these cables varies according to the nature of the sensors, but may serve to convey operating power to the sensors, to return signals from the sensors, to measure a physical quantity of the sensors (such as electrical resistance or the like), or as may be otherwise dictated by the kinds of sensors used.

Figure 1 also shows a power supply casing 40 within the housing, again mounted on its rear wall, containing a power supply transformer 42 by means of which suitable operating power is supplied, by cables (not shown) and under the control of the control means, to the various fans, and operating power for the control means and sensor means themselves are made available within the apparatus.

Figure 2 shows the principal elements of the control means 38 and the significant inputs and outputs. A circuit board 44 carries a microprocessor 46, which may either be programmable or provided with a suitably programmed read-only memory. Inputs to the microprocessor are provided through distinct channels by respective amplifier and interface circuits 50,52,54,56 received from the smoke, carbon monoxide, radon and humidity sensors 60,62,64,66. The inputs to the microprocessor amount to data, in that they may be digital data

streams or analogue measures of variables that are interpretable by the microprocessor as data values.

One output signal from the control means is taken to a power control output device 48 for the extractor fan 32, and a second output signal is taken to a power control output device 58 for the intake fan 34. These output signals may be simple commands to start or stop the fans, by adopting power on or power off conditions, but may include intermediate speed control commands. A third output is connected to an LCD display 68 in which panels 70 can be activated to spell out the nature of any air constituent or contaminant that may have triggered ventilation action, and to provide other read-out data for any other purpose, such as for programming the control means. A further signal output from the control means is used to activate an audible alarm 72, which may be supplemented by or replaced by a visual alarm or any other kind of alarm signal.

Figure 3 is a table of control means responses to a variety of atmospheric conditions detected by the sensor means.

In the table, the figures 1 and 0 respectively indicate whether the data received from the smoke, carbon monoxide, radon and humidity sensors indicate concentrations above or below an acceptable value. The values are in all cases displayed on the LCD display panels 70. Within the microprocessor 46, the values are accepted and interpreted according to whether they are sufficient to trigger a ventilation response and, in the case of smoke, carbon monoxide and radon, an audible alarm.

The response to detection of smoke above an acceptable ambient level is to demand both negative and positive ventilation, ie air extraction by the extractor fan 32 and air intake by the intake fan 34, an alarm status indication at the LCD display 68, and the triggering of the audible alarm 72.

The response to detection of carbon monoxide in the room air is to trigger

positive ventilation, that is to say the drawing in of extemal air by the intake fan, display of an alarm status, and triggering the audible alarm.

Response to a radon level detected above an acceptable ambient level is to initiate positive ventilation through the intake fan and to display a radon alarm status at the display panel.

Response to unacceptable levels of humidity is to initiate negative ventilation at the extractor fan, and to give the appropriate status indication at the LCD display.

The order of precedence of the responses to the data are that data relating to smoke is given the highest priority, overriding all other requirements ; carbon monoxide takes second place, overriding all requirements other than those arising from a response to smoke detection ; radon detection occurs at the third level of precedence, overriding all other requirements except those of levels 1 and 2, and humidity data occur at the fourth and lowest level of precedence, being overridden by the demands of all other levels.