what is preinsulated duct in HVAC.what are the products of combustion of it.is it harmful?
352952
A pre-insulated duct is a duct that is already covered in insulation such that insulation does not need to be added to an ordinary duct such as a galvanized one or a stainless steel one.\n\nThere are no products of combustion in a HVAC circuit. Take a fridge, the condenser at the back is warm whilst the evaporator inside the fridge cools it down. The compressor forces the refrigerant around the circuit. A thermal expansion valve is also involved and this determines the rate of evaporation. It is a continuous circuit, there are no combustibles.\n\nR134A is the latest refrigerant gas which is not as harmful as the R12 it replaced, however, all refrigerants are CFC's which should be recycled.
1183098
HVAC may also stand for High-voltage alternating current\n\nHVAC (pronounced either "H-V-A-C" or, occasionally, "H-VAK") is an initialism/acronym that stands for "heating, ventilation and air-conditioning". This is sometimes referred to as climate control.\n\nThese three functions are closely interrelated, as they control the temperature and humidity of the air within a building in addition to providing for smoke control, maintaining pressure relationships between spaces, and providing fresh air for occupants. In modern building designs, the design, installation and control systems of these functions are integrated into a single "HVAC" system.\n\nIn certain regions (e.g., UK), the term "Building Services" is also used and HVAC Engineers are called Building Services Engineers. See CIBSE.\n\nThe term air handler can mean a whole unit including the blower, heating and cooling elements, filter racks or chamber and dampers, but not including the ductwork through the building.
429253
If it generates more than 70ppm, then according to the EPA it is unsafe.  Personally, if you can smell the ozone, then it's unsafe.  This means that it's producing at least 30ppm.
170244
some kind of blockage in the duct
453848
A reformer is a huge furnace that provided the heat enery required to seperate the Hydrogen and Carbon from the stable CH4 molecule. \n\nThe ones I have worked with works like this:\nA mixture of the gas CH4 and steam H2O is passed thorough a tube that is filled with catalyst, that goes into the furnace (reformer) where it is heated to around 900C.\n\nAt that temp, and with the steam, the following are formed\nHydrogen, Carbon Monoxide, and Carbon Dioxide. So the carbon forms the CO and CO2.\n\nOther molecules can cause the following: Oxygen: Explosion\nNitrogen: Nothing\nSulpur: Kills catalyst.
863664
Well, it is a strong oxidant especially in an acidic form, so it could be a problem if it leaked onto anything combustible.  It is also very hazardous to health and environment, so accidental exposure can be a problem.   It will emit very toxic fumes in a fire situation, so it can be quite hazardous to firefighters, especially if they don't know its there.\n\nSome plastics may become brittle with age if it is stored too long, leading to breakage and leakage.\n\nI would say that is the biggest hazard, being accidentally exposed to to an improper containeer or labeling.
1107715
h-heating\nv- ventillation\na- air \nc- conditioning\nr- refrigeration\n\nrefrigeration is cooling the air\n\nconditioning is changing the state of the air \n(eg. humidity, pressure, volume, etc)
928685
An electric INCANDSCENT bulb uses a tungstene filament (twisted wire) that is heated by the current passing through to several hundred degrees.  It is this heat that heats the glass.  It is also the proof of inefficiency of the bulb, because it is transforming 80% of the energy it receives into heat, giving only 20% for light!\nIn the FLUORESCENT tubes, the light is produced by the ionisation of the internal gas (neon or argon).  This ionisation is initiated by heating two small filaments at teach end of the tube, that heat up a small drop of mercury.  Once the mercury is vaporised inside the tube, the "starter" opens, creating a high voltage puls across the whole tube, ionising the gas that then becomes conductor: a small current passes through the gas, and the filaments are disconnected.  Since the ionised and conductive gas has nearly no resistance, the current is limited by the "ballast" (an inductor inserted in series).\nSince the CURRENT is limited, there is no "Joule Effect" (heating) and the tube stays pretty cool.\nTheir efficiency is about 100 times more than a bulb... (in terms of power/light ratio).
128599
My understanding is that in those cases when there is a fire inside (typically in a "lamp", traditionally a stone vessel burning seal oil, or something, since there is not much vegetation in a lot of these places), that a chimney/ventilation hole is placed in the ceiling to let the smoke and heat out a bit. The second reference includes a drawing from Martin Frobisher's 1576-1578 expedition to Baffin Island, showing windows (which could also function as ventilation holes) in the igloos. Windows were traditionally made from fresh water ice, and were valuable enough that when the igloo was abandoned, the inuit took the window pane with them. \n\nThe previous response is also correct, I believe. Ice and snow are a good insulators (this is why lakes do not freeze solid very often even when it is very very cold). Therefore, not a lot of heat is required to make an igloo quite warm inside, even when the temperature outside is very cold. Why doesn't the igloo melt? There is a substantial heat of fusion that is required to melt snow or ice. The radiant heat from the fire just melts the inner layer of snow to create an ice glaze. Most of the heat is reflected back as well because of the color of the snow. \n\nI have attached a reference from a person who did some experiments with igloos.
471285
convection is the transfer of heat by the flow of air. Duct tape prevents air from flowing outside of the ducks.
671063
Noiseless sparking can create O3. However a parking fan is also a hazard to live with, not to mention that the O3 produced will be insignificant and any produced would attack the fan's motor.
881581
I have two opinions about your question   one is Radient heatbarrier and reflection house insullation  or Icyene spray foam insulation   reason being they keep down on modern day cost efaicante  heating and cooling bills during the summer and winter.
199036
Current burns, voltage jerks the muscles.  Too much current, you're toast.  Too much voltage, your heart stops.\n\nStatic built up from rubbing your socks on the carpet probably won't kill you.\n\nSeveral years back, in the wintertime, there were some news reports of people whose car blew up at the gas pumps.  Supposedly it was due to static electricity.\n\nIt's rare to get "shocked" outside when getting in or out of one's car or touching it or whatever but it does happen.  I remember a couple times in the past 5 years when it happened to me. A tiny percentage of times I have done that but way more than zero.\n\nSo, I guess the combination of a spark and being by your open gas tank could kills you, indirectly.\n\nTaking an extreme counter-example, there was a girl struck by lightening at the WHFS alternative rock festival in DC a few years ago. Apparently it knocked her a few feet from where she was standing.  But, it didn't kill her.  She was lucky.\n\nStatic charges build up more easily in wintertime. The air is dryer.  Something about the air molecules is different when there is less moisture.  I forget what, but you have probably noticed more "static" shocks in winter than any other time of year, unless you live in a really cold, dry place.\n\nA three inch spark seems pretty far.\n\nIn high school physics class, they said that each inch that a spark travelled off a sphere through the air indicated 10,000 volts.  I think it was 10,000.  Well, you're not a sphere and you are probably not touching one but that still seems like a lot.\n\nI used to get shocks of half or three quarters of an inch  when touching the corners of walls at the house I grew up in all the time.  That was really nothing.  I barely felt it.  It was just a surprise to feel it, and also to see the spark leap between the wall and your finger.\n\nModern buildings have grounding wires on all the outlets and stuff like that, to prevent electrical problems.  Not sure what really old buildings are like.\n\nIf you are wearing a sweater or wool clothing, that could increase the amount of static charge you build up.  There are all kinds of things that could do it.\n\nIf it happens on warm, humid days when you are not wearing any wool or sweaters, that would really be strange.  If not, maybe it is what you are wearing or the atmosphere that is mostly responsible.\n\nAlso, carpet is a big factor.\n\nFeeling it hours later, that's freaky. That never happened to me.
800927
dont know about q1\n\nQ2 They push the heat out at the floor because the coler air is at the bottom of the floor and since hot air rises then then the hot air will circulate more by rising through the cooler air and warming it up as opposed to being near the ceiling where the hot air would just stay near the ceiling.\n\nQ3 The smoke is usually heated and composed alot of carbon monoxide. The heated smoke will rise as it is warmer than the cooler air around it, once it cools down to the temperature around it than it will usually fall back down since carbon monoxide is heavier than air and that it will also combine with other elements in the air.\n\nQ4 A continuous hot water system works better because the the hot water is circulated throughout whatever system it is heating, such as air or other water then return back to the heater (furnace) not cooled completely and still retaining some of the heat it originally had and since it is already warm it takes less energy and time to heat it back up to its original temperature.
322538
It may depend on the source and use of heat.  An electric heater would heat the air locally permitting the air to hold more moisture while perhaps drying some surfaces, but would not remove any moisture.  An existing circulation air heating system placed into service by opening duct vents would supply new dry air forcing moist air to move on perhaps returning to the furnace.  The basement may be damp because moisture penetrates the walls (possibly through cracks).  Therefore a dehumidifier or a central heating system may perform equally well compared to an electric heater unless the electrically heated warmed air is free to leave the area (perhaps rising up the stairs?).
977199
Which is safer?...  plenum cable, always.\n\nThis is especially true where it's being run inside an air circulation cavity (or "plenum")  -such as the attic or in an air duct, because it's fire-retardant.\n\nRegular riser cable is just PVC, and should never be used in any space where air circulates.\n\nFor a domestic installation, just use plenum cable throughout, and sleep a little easier.\n\nOn a related note... be very careful about penetrating fire walls to run cables.  If you absolutely must, be sure to use a fire-resisting sealant, and check with your local building codes
506524
The vast majority of air conditioning systems do not purify air.  There are a few that do however.  Some air conditioning units are equipped with HEPA filters.  These filters filter out quite a lot of small particles.  Some use activated-charcoal which is able to chemically react with many potential toxins in the air.  Others use UV light inside the air conditioning unit in order to break down particles of pollen, viral particles, bacteria, and fungi.  I am unaware of any that can remove CO2, but there are some that can probably remove CO.  Some do unfortunately produce ozone.\n\nThe units that use UV light can produce ozone, and sometimes can even blacken walls where they pump out air.  Some filters use charged plates to capture charged particles in the air.  These charged plates can also cause the formation of Ozone.