Hello Farmers, hope you are all copasetic today.
I wanted to get a discussion going about IR cameras (specifically FLIR-forward looking Infra Red used by police) and the myths surrounding them as many a grower seem to worry about police helicopters using this tech to detect their grow rooms. I myself have heard people use this a the sole reason for not growing their own Buddha.
So the myth is that -IR cameras can see through walls.
Although a common belief in hollywood this is simply not the case. Infra red Cameras can only detect heat via the IR radiation eminating from it so unless something hot or the air on the other side of the wall is hot and therefore warming the wall itself then an IR camera simply can NOT see through walls or any other solid / liquid object for that matter.
This is demonstrated abundantly by those Police Cop Action shows, ever seen IR footage of a helicopter chasing down a suspect - funny how the glowing red image of his body heat disappears whenever he goes under a tree or in a house or even gets in a car. but when the guy (or gal in somecases!) stops for any length of time their body heat will warm, via conduction, whatever they are touching and this will show up on camera provided there isnt something else in between the camera and hot object.
so hopefully clearing that up i want to move the topic on to risks for growers specifically and possible ways of minimising said risk. The problem is that in most setups there will be alot of warm air generated by the lighting and it is this that makes it hard to mask the IR sig of a grow op, well that and warm objects conducting their heat to other objects.
it may help if i clear up a few facts before going any further - this is abit basic so you may want to skip but for those not up on their science may find it useful.
heat can travel by three ways only
Conduction - you touch something hot with finger, heat from the object is transfered from it to your finger and consiquently your finger warms up.
Convection - fundamentally the same as conduction but instead of direct contact it uses a gas (ie. Air) to transfere heat. this is how the incorrectly named 'radiator' in your home works.
Radiation - this is what Infra Red is and is a form of electromagnetic radiation that travels in waves emitted from any object above -273c (absolute zero) in all directions much like the filament in a light bulb, it needs no medium to travel but is slowed or halted by just about every form of matter of varying amounts including liquids and gases. for example this is how the Sun gets its heat to our planet through 93,000miles of complete vacuum. A curiuos thing really as is not hot istself but will cause objects to heat up on contact, ie the difference between ambient temperature and radiant temperatue is caused by IR.
To make it clear you can NOT get rid of IR radiation without eliminating the heatsource itself - this would break the laws of physics, but as FLIR gives off no emmisions itself but merely picks up external emmisions you can mask you IR sig by using certain materials and making sure nothing warm is touching the outer walls of where you grow thus lowering your overall emmision of IR. Also if using a fan to vent externally the longer the ducting the better as this gives the unwanted air the chance to return to ambient temps and will be less visible on FLIR - this is arguably the largest area of concern for any wanting to mask their IR sig.
Thought also must be given to where you grow, in a house is the safest bet and is nigh undetectable to FLIR as 99% of everything used in housing construction is designed to block heat transfere therefore IR aswell, things like insulation, the cavities in walls, double glazing -the list goes on.. coupled with the amount of exsisting heatsources in a domestic enviroment make it very difficult to detect a grow light.
People who grow in an outdoor solitary building, like a garden shed for example are most at risk from IR detection as there is more chance of heat conducting from one object to another and eventually raising the temps albeit slightly of the outter walls which WILL be visible to any FLIR thermographer hovering above.
For those growing in outhouses/sheds and the like as long as your grow room walls are ambient to the touch on the outside which is easily acheived by wrapping the room in some type of insulation, ThermaFoil for example. And the air temps around your grow area (not the grow room itself) arent excessively above ambient then your thermal signiture will be masked by ambient thermals completely.
Also putting glass pains around the outside of your grow room ontop of a layer of insulation is a good idea as its good at dissipating IR, i myself put a large bedroom mirror ontop of my grow room, however it is a good conductor of heat so make sure its not touching anything warm or the glass itself with start to generate more IR than ambient.
Anyway i hope this clears some of the fallicies revolving this technology and more importantly eases people's conscience on the matter.
Peace
