GB2532741A

GB2532741A - Method and apparatus for monitoring fog density

Info

Publication number: GB2532741A
Application number: GB1420927.4A
Authority: GB
Inventors: John Pendred Christopher; Pendred Guy
Original assignee: NORMAN PENDRED AND Co Ltd
Current assignee: NORMAN PENDRED AND Co Ltd
Priority date: 2014-11-25
Filing date: 2014-11-25
Publication date: 2016-06-01
Also published as: GB201420927D0; WO2016083792A1

Abstract

A fog density monitor 1 comprises means to indicate fog density and forward data to a controller. A system for monitoring and controlling fog density further comprises a fog delivery apparatus (300, Fig 3) and a controller for controlling the delivery of fog in response to the fog density data. The system finds application in maintaining the freshness of produce by promoting natural hydration and distributing biocides. The monitor may comprise an infrared transmitter 25 arranged opposite a receiver. The system may comprise a plurality of monitors 1 and delivery apparatuses (300, Fig 3), as well as a plurality of fans to maintain uniform fog density. The fog may be dry fog and may be generated by piezoelectric ultra-sonic nebulisation. The fog or mist may include a chemical agent such as a biocide or plant food.

Description

Method and Apparatus for Monitoring Fog Density The present invention relates to a system, including an apparatus and method, for monitoring adjusting and maintaining one or more levels of generated fog density in an enclosed or partially enclosed space.

Products, or fresh produce, are often stored for periods of time and it is important that they remain as fresh or free from spoilage as possible. Such spoilage can be the result of, for example, exposure to micro-organisms such as viruses, vegetative bacteria, spore forming bacteria, fungi, prions and other pathogenic micro organisms. It can often be desirable to prevent contamination by other agents also. Regardless of the produce, it is generally essential to maintain a minimum quality during the storage period, so that at the end of the storage period the produce is edible or otherwise usable. For produce such as potatoes or other root vegetables, this often requires action to suppress sprouting, whereas for other crops such as salads, vegetables, flowers, or fruit, quality is maintained by promoting natural hydration, thereby increasing plant turgidity, or preventing spoilage through dehydration, loss of moisture or turgidity, or by reducing the effect of spoilage bacteria, moulds, fungi or other spoiling agents.

Conventionally such produce is placed in a temperature controlled enclosed or semi-enclosed space and may also be subjected to treatments to suppress or destroy the spoiling agents, or to hydrate the produce. Such treatments include vaporising, spraying, fumigating and fogging, including mechanical fogging in agriculture, of liquid preparations. In particular piezoelectric ultrasonic nebulisation of such liquid preparations is often used, for example in agriculture as a post harvest crop hydration system to maintain the life of living plants for days, weeks or months after harvest, or in other situations.

It is often important that the product or produce, or the walls, floor, ceiling, fixtures and fittings of the space used for storage, do not become wet when subject to these treatments. It is possible to avoid such wetting by delivering such treatments by means of a 'dry fog' to the space and its contents. The dry fog comprises a visible mist of droplets of liquid that are less than 5 microns in diameter.

In addition, it would be useful to develop a methodology or protocol which could be relied upon to predict the values of the respective parameters that need to be set, given the product or produce to be treated, the time for which storage is contemplated, and the volume in which it is stored. For example it would be useful to be able to establish the concentration of a biocide, the density of a dry fog, the treatment delivery time, the temperature, and the values of other parameters for example the 10 treatment protocol or cycles that would be needed to achieve a desired outcome in terms of product quality or spoilage reduction for products or produce to be stored for a predetermined time in a predetermined space.

While it is possible to maintain certain variables such as a particular treatment time and temperature in a variety of settings, other parameters such as fog density can be problematic.

It would therefore be advantageous to provide an arrangement for maintaining a predetermined density of fog uniformly throughout a space over a timeseale.

According to a first aspect, the present invention provides a fog density monitoring system for monitoring fog density in a space, the system comprising at least one fog delivery apparatus, at least one fog density monitor, and a controller in communication with the at least one fog delivery apparatus and the at least one fog density monitor. The fog density monitor is designed to monitor fog density and provide fog density data to the controller, and the controller, responsive to fog density data, controls delivery of fog from the fog delivery apparatus to the space.

Preferably the at least one fog density monitor comprises a plurality of fog density 30 monitors, distributed uniformly around the space, each in communication with the controller.

Preferably the least one fog delivery apparatus comprises a plurality of fog delivery apparatus distributed uniformly around the space, each in communication with the controller.

Preferably the controller, responsive to the fog density data from a, or from each, fog density monitor, controls delivery of fog from a, or from each, fog delivery apparatus.

Preferably the fog delivery apparatus generates a dry fog.

Preferably the dry fog comprises droplets of less than 5 microns in diameter.

Preferably the dry fog is generated by a piezoelectric ultra-sonic nebulisation process.

Preferably the fog includes a chemical agent, which may be a biocide, a plant food, or a Bio-flavonoid for folia feeding.

Preferably the system further includes at least one fan in communication with the controller, wherein the controller, in response to fog density monitor data, actuates the at least one fan to urge fog around the enclosed space to maintain a desired uniform fog density.

Preferably the at least one fan comprises a plurality of fans.

According to a second aspect the present invention provides a fog density monitor 25 comprising means to detect a fog density adjacent the monitor, and means to indicate the fog density and forward same to a controller.

Preferably the means to detect a fog density comprises a transmitter adapted to transmit a signal, and a receiver adapted to receive the transmitted signal.

Preferably the means to indicate fog density further comprises the transmitter adapted to provide the controller with information regarding the transmitted signal, and the receiver adapted to provide the controller with information regarding the received signal.

Preferably the fog density monitor further comprises means to receive a benchmark 5 value of fog density, means to compare detected fog density with the benchmark value and determine a deviation of detected fog density from the benchmark, and means to forward an indication of said deviation value to the controller.

According to a third aspect, the present invention provides a method of monitoring fog density in a space comprising positioning at least one fog density monitor, connected to a controller, within the space, positioning at least one fog delivery apparatus, connected to the controller, within the space, operating the controller to monitor fog density data received from the at least one fog density monitor and instruct the at least one fog delivery apparatus to modify fog delivery in response to data from the at least one fog density monitor.

Preferably the at least one fog density monitor comprises a plurality of fog density monitors positioned uniformly around the space, and the at least one fog delivery apparatus comprises a plurality of fog delivery apparatus provided uniformly around the space.

Preferably the space is an enclosed or a semi enclosed space.

Preferably the method further includes providing at least one fan, connected with the controller, the controller operative to control the at least one fan to urge fog around the space to maintain a desired uniform fog density.

Preferably the at least one fan comprises a plurality of fans.

Preferably the method further comprises providing a fog including a chemical agent, and wherein the chemical agent may be a biocide, plant food or Bio-flavonoid for folia feeding.

According to a fourth aspect the present invention provides a controller, connectable with a fog density monitor and a fog delivery apparatus, adapted to control the density of a fog provided to a space by the fog delivery apparatus, responsive to the fog density monitor, to maintain a desired density uniformly throughout the space over a predetermined time period.

Preferably the controller is adapted to control the density of a fog responsive to data from a humidity sensor and thermometer.

A preferred arrangement of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a fog density monitor in accordance with the current invention, Figures 2(a) and (b) show details of a fog density monitor, and Figure 3 shows an arrangement of fog density monitors and fog delivery apparatus in a storage space.

Referring to the figures there is disclosed in Figure 1 a fog density monitor 1 including a base 10 including within itself a variety of electrical components including a central processor, and a plate 2 on which are mounted for example an infra red light emitter 25 and an infra red light detector 26. The monitor 1 may be battery or mains powered, and is connected, via cable 20, to a controller (not shown). Alternatively the fog density monitor 1 may be adapted to send information to the controller wirelessly.

In operation, a beam of infra red light of known intensity is directed from the emitter 25 towards the receiver 26. Any droplets of fog present between the emitter and receiver will refract the infra red beam and degrade the signal. The amount of degradation of the received signal is calculated by the central processor in, for example, the monitor. The central processor converts the signals between the emitter and receiver 26 into a signal of between 0 -10 Volts corresponding to 0 -100% fog density, calibrated such that a perceived 100% fog density will result in a 10 Volt signal, and no fog at all will result in a 0 Volt signal. In particular, it is contemplated that the signal of between 0 -10 Volts is interpreted by a central processor in terms of a 0 -100% True Fog Density (TFD) scale in which a 0 Volt signal corresponds to no fog detected, a 5 Volt signal corresponds to a 50% TFD, and a 10 Volt signal corresponds to a 100% TFD. Thus the electric signal of 0 -10 Volts provides a reading for the central processor of 0 -100 on the TFD scale.

Electronic compensation has been included within the design of the fog density sensor to allow it to be used in a variety of challenging environmental conditions.

Each of the emitter 25 and receiver 26 comprises a casing 30 covering a pipe 40, the pipe in communication with the interior of the monitor base and extending therefrom to a pipe end 60. Respective pipes 40 of each emitter 25 and receiver 26 pairs are positioned and arranged such that an end 60 of each pipe of the pair is facing an end 60 of the other pipe of the pair. The pipe ends 60 are sloped such that the distance from one pipe end to the other increases in the direction of the plate.

Figures 2 (a) and (b) show a detail of one of the emitter/detector units, including pipe 40 and pipe end 60. Pipe end 60 includes a transparent closure 65, which may seal the pipe. The monitor is adapted to generate a beam of infra red light to be transmitted through the transparent closure of a first one of the pair of pipes, the emitter 25, the monitor adapted to direct the beam of infra red light towards the transparent closure of the second one of the pair of pipes, the receiver 26. As stated, it is known that a beam of infra red light passing through a fog will be affected by the fog droplets, resulting in degradation of the beam, and the amount of degradation is directly related to the density of fog. Thus the degradation of signal detected when the infra red beam passes through the fog will provide an indication of the density of fog between the two pipe ends. The fog density detected will provide an indication of the fog density local to the fog density monitor.

Having a sloped pipe end will increase the surface area of the transparent closure and thus increase the sensitivity of the signal detection, providing for a more accurate determination of the value for fog density. In addition, as stated, the sloped nature of the pipe ends means that the distance between the pipe ends increases in the direction of the monitor, and thus the distance travelled by the beam of infra red light differs between the top of the pipe end and the base of the pipe end. This difference can also increase the sensitivity of the signal detection and provide a more accurate determination of the value for fog density.

The fog monitor detects the degradation in the signal between the two pipe ends and is adapted to transmit this information to a controller via cable 20, or by other means.

The controller (not shown) can then, dependent on the information received in relation to fog density, control a fog delivery apparatus to control delivery of fog to the space to maintain a desired fog density. If the fog density is too high the fog delivery apparatus can reduce the amount of fog being delivered or activate a defogging system (not shown). If the fog density is too low the fog delivery apparatus can increase the amount of fog being delivered.

Thus we have a system in which a fog density monitor detects a fog density local to the monitor, and forwards the fog density information to a controller which, responsive to said fog density information, controls a fog delivery apparatus to deliver a required amount of fog to achieve a desired fog density.

A single fog density monitor providing information to a controller to control delivery of fog from a fog delivery apparatus would be suitable for small spaces and small amounts of produce. However, many spaces which store produce arc large or very large.

In a further embodiment, several fog density monitors may be distributed around a space, together with several fog delivery apparatus or de-fogger. Each monitor is connected to a central controller which, on receipt of the information from all the monitors and, dependent on the respective fog density values in the space, controls the fog delivery apparatus to deliver respective amounts of fog or activate the de-fogging device such that a desired uniformity of fog density is achieved and maintained in the space.

Figure 3 shows several fog density monitors 1 distributed around a space, for example an agricultural glass house 40, and further shows a plurality of fog delivery apparatus 300 distributed around the space. The fog delivery apparatus 300 are shown to be different heights, to ensure that the fog delivered is maintained throughout the space.

It is contemplated that all the fog density monitors 1 and all the fog delivery apparatus 300 are connected to a single central controller (not shown) which monitors the fog density throughout the space and controls delivery of the fog via the fog delivery apparatus 300 throughout the space. For example if the fog density in one corner of the glass house is less than a desired amount, the fog delivery apparatus adjacent that corner will be activated by the controller to deliver more fog to bring the density back to the desired or required value. If the fog density in that corner is more than the desired amount, the fog delivery apparatus adjacent that corner will be controlled by the controller to reduce the amount of fog delivered until the density returns to a desired or required value.

On occasion the controller will detect that the fog density in one portion of the space is too high, but the fog density in another portion, possibly an adjacent portion, is too low. Redistributing the fog would provide a means to overcome this problem promptly and so in accordance with another embodiment, the system is provided with one or more fans, electrically controlled by the controller to urge fog from one position to another in the space, rather than to reduce the fog delivered by one fog delivery apparatus and increase the fog delivered by another fog delivery apparatus.

While a fog density monitor may determine a local fog density by detecting the degradation in signal from end 60 of one pipe of a pair to end 60 of the other pipe of the pair, other factors may influence signal degradation. For example, fog droplets may coalesce on the transparent closure of each pipe end. To avoid signal degradation due to fog coalescing on the transparent closure, the light emitter and light receiver, and also possibly the transparent closure, may be heated to reduce or eliminate such effects.

The, or each, fog density monitor provides data to the controller indicating the fog density local to the monitor. Such fog density data can be provided as an absolute value determined by the detected signal degradation, and the controller will then determine the additional fog, or reduced amount of fog, that needs to be delivered to each location to bring the reading or readings into line with desired values, and control the fog delivery apparatus, or fans, accordingly.

Alternatively each fog density monitor may be provided by for example visual calibration with a desired reading for fog density, and further provided with the means to compare this desired fog density with the actual local fog density determined from signal degradation. Each fog density monitor may then provide an indication to the controller of the extent to which the determined local fog density fails to match the desired fog density, set as required into the control unit, and thereby an indication of, for example, the percentage by which the determined local fog density fails to match the desired fog density, allowing the controller to instruct respective fog delivery apparatus to deliver additional, or less, fog, or activate fans or activate the de-fogging device to reduce the density of fog that has been equalised by the fans, to bring the readings into line, It is contemplated that this method provides a faster and potentially more accurate means to achieve the desired fog density.

When products or produce are to be treated, for example during storage or at any time, it is generally straightforward to establish the quantity of product or produce to be treated, the space to be treated, the temperature at which the product or produce is to be stored, the length of time for the treatment, and the concentration of biocide needed, if used, however it is not so straightforward to maintain a fog density over the time period of a treatment, or to establish a confidence as to the fog density that was operative and to which the product or produce was exposed, during the treatment period. The present invention addresses this problem and provides for the fog density to be calculated and maintained over any time period.

In addition, it is often necessary, when establishing the efficacy of a particular biocide, to test the biocide under controlled conditions. Hitherto it has not been possible to establish the efficacy of biocides under all required conditions as it is not possible to ensure that a desired, controlled, density of biocide, delivered in a 'dry fog', has been used.

In accordance with the present invention it will be possible to control sufficient parameters of any test environment, including the sustained density of a dry fog containing such a biocide, such that for example the efficacy of a biocide can be established compared, for example, to other biocides under the same conditions.

It would be very useful both in agriculture, and in a variety of other commercial enterprises, to be able to follow a defined protocol with a predictable outcome for stored products or produce. Also to store data from the controller that can be reviewed to show or validate that a treatment protocol has been correctly applied.

In particular the present invention provides for a variety of trials to be carried out, which will allow for protocols to be established. The protocols can then be relied upon so that a user, for example wishing to achieve or maintain a desired condition of stored products or produce, will be able to refer to and follow the protocol and have a predictable degree of confidence that the product or produce will, at the end of the storage period, have a certain standard of freshness, or avoid spoilage to a desired standard. The protocols will also provide a margin of error, and also the opportunity to record the procedure followed. For example the present invention provides the opportunity for a user or storage facility to transmit and or record treatment data 20 including fog density and show that a treatment cycle or protocol has been followed. If a negative outcome ensued, it would be helpful for the storage facility to be able to show that the required treatment protocol had been followed. This would ensure security for the treatment facility and confidence that the required functions had been performed.

In use the product or produce to be stored may be placed in a storage space with a fog density monitor and a fog delivery apparatus, both of which are connected to a controller. If the produce needs to be treated with a biocide then the amount of biocide for the produce type, the produce quantity, and the time for which the produce is to be stored may be calculated. The biocide may then be prepared and nebulized to produce a dry fog in the space. If the produce does not need to be treated with a biocide but needs only to be hydrated, calculations based on that treatment may be carried out. The fog density monitor detects the local density of fog, biocidal or otherwise, and passes this information to the controller, which controls the fog delivery apparatus to deliver the biocidal or other fog to the desired density, or operates a fan or fans to redistribute the fog within the space. The fog density is monitored by the fog density monitor continuously and thus the fog is maintained for the desired period at a desired or required density to achieve the hydration or biocidal effect needed to ensure the standard of freshness desired for the produce at the end of the storage period. Also any level of wetting or condensation on the surfaces of products or equipment within the space can be controlled. The wetting or condensation can be controlled by controlling the amount of fog being produced, for example by preventing too much fog being produced, or by controlling the temperature.

Where the quantity of produce to be stored requires a larger storage space, or where only a larger storage space is available, a uniform fog density can be maintained throughout the space by distributing several fog density monitors around the space. In addition, several fog delivery apparatus are distributed around the space also. All the fog density monitors and fog delivery apparatus are connected to a controller, which monitors data received from the fog density monitors and controls the delivery of fog to the space to ensure that a desired fog density is maintained throughout the space.

In addition, the controller may also be connected to one or to several fans, and may utilise the fans to ensure a uniform distribution of fog within the space.

The space may be a warehouse, an agricultural glasshouse, poly tunnel, a rapid chiller, cold store, a supermarket cold store or other storage environment. It is clear 25 that some of the parameters determining the density of fog will vary during the storage period, and the present arrangement compensates for such variations.

For example, where the storage area is an agricultural glass house or a green house, the sun may shine through the glass in certain places, at different times of the day, and locally heat the air adjacent those places, leading to a variation in temperature over the space. This is important because the amount of vapour/gas that air can hold is dependent on temperature. The higher the temperature the more vapour/gas the air can hold, however as the temperature increases so the less than 5 micron droplets of the present dry fog are increasingly inclined to evaporate into vapour/gas, resulting in a reduction of droplets in the air and therefore fog density. In addition, when for example the glass house or greenhouse door opens, or for example at night, the temperature locally may drop, resulting in a reduction in the amount of moisture that the air can hold, and an increase in the density of droplets, which may cause wetting.

In areas where the temperature becomes lower the density of droplets may become greater, so that droplets may coalesce and drop onto the floor, or 'wet' surfaces. It is generally necessary to subject produce to a specific density of fog, for example for hydration, or to utilise a biocide or other chemical effectively, for a specific time period, to ensure a predictable outcome in respect of produce quality, and therefore it is very important to have a system that dynamically responds to environmental changes to maintain the required hydration or biocide delivery.

Where the storage area is a rapid cooler cold store for example, conditions may vary during an essential refrigeration defrost cycle, or the temperature may also vary for example if a door is opened or left open, and the present system provides a dynamic response to any reduction in fog density, to bring the fog density back to the required level.

As stated before, it may be that the controller has access to one or a number of fans which the controller can utilise to urge fog from an area with a high fog density to an area with a lower fog density to assist in the maintenance of a uniform fog density throughout the space.

In addition, produce may be stored for extended periods of time, for example days, weeks, or months. A biocidal treatment is unlikely to be continuous for a long period of time but may operate at intervals, for example for perhaps 3 hours out of 24 although other cycles are contemplated and fall within the scope of the present invention. The treatment may include several different cycles, for example a cycle with a biocide, a cycle with water, an organic acid or other fluid. The cycles may even include periods with no fog at all. Using the present system a degree of confidence can be established and maintained that the correct cycles have been followed and treatments, in particular for example standardised treatments, applied.

For example, it would take about 4 hours to fill an 8 hectare agricultural glass house with a sanitising dry fog of a required density. A typical treatment cycle may subject the storage area and produce contained therein with a prescribed density of an ECAS (electro-chemically-activated solution) of a prescribed concentration, for, for 5 example, 3 hours, after which it would be necessary to maintain a 90% humidity without the biocide. The present invention provides a straightforward mechanism by which all these parameters could be met with a predictable confidence.

An additional advantage of the present invention is that the process may be entirely automated. For example, the, or each, fog density monitor and fog delivery apparatus may be provided to a storage area and connected either directly or wirelessly to a controller. The parameters influencing the treatment cycle may then be controlled automatically, or remotely -in particular without the need for anyone to enter the storage area. This may be vitally important if the biocide used is toxic, or otherwise dangerous, to humans if over exposed.

A further advantage is that the present invention is economical in terms of cost and also environmental impact. In particular, the particular biocide used is often an expensive part of any treatment, and the amount of biocide that is used effectively is often a small percentage of the biocide applied. Some biocide may end up on the floor and walls if droplets coalesce, some biocide may be lost through evaporation, or more fog (including biocide) may be applied than is needed. This can be expensive in monetary terms and may also be harmful to the environment as the biocide will end up in the environment in some manner or other. The present invention provides a mechanism and system to finely time the required amount of biocide, and reduce waste.

The present invention has the still further advantage that it may allow for calibration and testing of ECAS (electro-chemically-activated solution).

The present invention has the considerable advantage that information from a fog density controller, possibly together with a humidity sensor and thermometer, may be used to control an environment in which products, or produce, may be stored to a predictable and quantifiable standard.

In particular a variety of liquids may be nebulised into a fog for delivery to the products of produce, the liquids being converted into a fog of a pre-set density. The arrangement allows for a number of time periods or cycles to be programmed and followed. The variety of nebulised liquids, and the density of fog the variety of nebulised liquids provides, may be delivered for a variety of pre-set times, enabling a treatment regime to be repeated as required. The treatments may include for example hydration of living plant cells, the reduction of de-hydration while controlling the growth of living organisms such as for example bacteria, spores, or viruses, the sanitisation of both living plants, salads, or vegetables and also slaughtered meat such as for example beef, chicken, lamb, pork, and so on, the sanitisation of the air in an enclosed or semi-enclosed space, and the sanitisation of the walls, floor, food storage bins, racking, hanging rails, conveyor systems, or other food processing equipment fitted to or positioned in the enclosed or semi enclosed space, and other suitable applications.

The invention is not restricted to the details of the foregoing examples. For example 20 the light emitter and receiver pair positioned on the fog density monitor are disclosed as an infra red emitter/detector pair; however they may rely on an alternative wavelength of electromagnetic radiation, or an alternative energy source entirely.

In addition, while we have referred to a sanitising fog, and to ECAS, it is also contemplated to cover organic acids, plant food, Bio-flavonoid for folia feeding, or other suitable solutions. Also, while the calibration referred to in respect of providing a fog density monitor with a desired reading for fog density is a visual calibration; such calibration need not be by visual calibration but may be by an alternative suitable means familiar to one skilled in the art. In addition, the controller may also be adapted to control the density of a fog responsive to data from a humidity sensor, and/or from a thermometer.

Claims

Claims: 1. A system for monitoring and controlling fog density in a space comprising: at least one fog delivery apparatus, at least one fog density monitor, a controller, in communication with said at least one fog delivery apparatus and said at least one fog density monitor, wherein said fog density monitor is adapted to monitor fog density and provide fog density data to said controller, and wherein said controller, responsive to said fog density data, controls delivery of fog from said fog delivery apparatus to said space.
2. The system of claim 1, wherein said space is an enclosed, or a semi-enclosed, space.
3. The system of claim 1, wherein said at least one fog density monitor comprises a plurality of fog density monitors, distributed uniformly around said space, each in communication with said controller.
4. The system of claim 1, wherein said at least one fog delivery apparatus comprises a plurality of fog delivery apparatus distributed uniformly around said space, each in communication with said controller.
5. The system of claim 1, wherein said controller, responsive to said fog density data from a, or from each, fog density monitor, controls delivery of fog from a, or from each, fog delivery apparatus.
6. The system of claim 1, wherein said fog delivery apparatus generates a dry fog.
7. The system of claim 6, wherein said dry fog comprises droplets of less than 5 microns in diameter.
8. The system of claim 7, wherein said dry fog is generated by a piezoelectric ultra-sonic nebulisation process.
9. The system of any one of the preceding claims, wherein said fog includes a chemical agent.
10. The system of claim 9, wherein said chemical agent is a biocide, a plant food, or Bio-flavonoid for folia feeding.
11. The system of claim 1, wherein said system further includes at least one fan in communication with said controller, and wherein said controller, in response to said fog monitor data, actuates said at least one fan to urge said fog around said enclosed space to maintain a desired uniform fog density.
12. The system of claim 1, wherein said at least one fan comprises a plurality of fans.
13. A fog density monitor comprising: means to detect a fog density adjacent said monitor, and means to indicate said fog density and forward same to a controller,
14. The fog density monitor of claim 13, wherein said means to detect a fog density comprises a transmitter adapted to transmit a signal, and a receiver adapted to receive said transmitted signal.
15. The fog density monitor of claim 14, wherein said means to indicate said fog density further comprises said transmitter adapted to provide said controller with information regarding the transmitted signal, and said receiver adapted to provide said controller with information regarding the received signal.
16. The fog density monitor of claim 14 or claim 15, wherein said signal is an infra red beam.
17. The fog density monitor as claimed in claim 13, further comprising: means to receive a benchmark value of fog density, means to compare said detected fog density with said benchmark value and determine a deviation of said detected fog density from said benchmark, and means to forward same deviation value to said controller.
18. A method of monitoring fog density in a space comprising: positioning at least one fog density monitor, connected to a controller, within said space, positioning at least one fog delivery apparatus, connected to said controller, within said space; operating said controller to monitor fog density data received from said at least one fog density monitor and instruct said at least one fog delivery apparatus to modify fog delivery in response to data from said at least one fog density monitor.
19. The method as claimed in claim 15, wherein said at least one fog density monitor comprises a plurality of fog density monitors positioned uniformly around said space, and said at least one fog delivery apparatus comprises a plurality of fog delivery apparatus provided uniformly around said space.
20. The method as claimed in claim 15, wherein said space is an enclosed or a semi enclosed space.
21. The method as claimed in claim 15, wherein said method further includes providing at least one fan, connected with said controller, said controller operative to control said at least one fan to urge fog around said space to maintain a desired uniform fog density.
22. The method of claim 15, wherein said at least one fan comprises a plurality of fans.
23. The method of claim 15, further comprising providing a fog including a chemical agent.
24. The method of claim 15, further comprising providing a fog including a biocide, a plant food, or a Bio-flavonoid for folia feeding.
25. A controller, connectable with a fog density monitor and a fog delivery apparatus, adapted to control the density of a fog provided to a space by said fog delivery apparatus, responsive to said fog density monitor, to maintain a desired density uniformly throughout the space over a predetermined time period.
26. The controller as claimed in claim 24, wherein said controller is adapted to control the density of a fog responsive to data from a humidity sensor and thermometer.