What is Fire: Definition and 305 Discussions

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products.
Fire is hot because the conversion of the weak double bond in molecular oxygen, O2, to the stronger bonds in the combustion products carbon dioxide and water releases energy (418 kJ per 32 g of O2); the bond energies of the fuel play only a minor role here. At a certain point in the combustion reaction, called the ignition point, flames are produced. The flame is the visible portion of the fire. Flames consist primarily of carbon dioxide, water vapor, oxygen and nitrogen. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, and any impurities outside, the color of the flame and the fire's intensity will be different.
Fire in its most common form can result in conflagration, which has the potential to cause physical damage through burning. Fire is an important process that affects ecological systems around the globe. The positive effects of fire include stimulating growth and maintaining various ecological systems.
Its negative effects include hazard to life and property, atmospheric pollution, and water contamination. If fire removes protective vegetation, heavy rainfall may lead to an increase in soil erosion by water. Also, when vegetation is burned, the nitrogen it contains is released into the atmosphere, unlike elements such as potassium and phosphorus which remain in the ash and are quickly recycled into the soil. This loss of nitrogen caused by a fire produces a long-term reduction in the fertility of the soil, but this fecundity can potentially be recovered as molecular nitrogen in the atmosphere is "fixed" and converted to ammonia by natural phenomena such as lightning and by leguminous plants that are "nitrogen-fixing" such as clover, peas, and green beans.
Fire has been used by humans in rituals, in agriculture for clearing land, for cooking, generating heat and light, for signaling, propulsion purposes, smelting, forging, incineration of waste, cremation, and as a weapon or mode of destruction.

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  1. sbrothy

    What Does Three-Alarm Fire Indicate in Emergency Codes?

    This may seem like a stupid question but it's been puzzling me for some time. I've read stories in English where fires are referred to as, for instance, a three-alarm fire or a four-alarm fire and I just now met the concept again. What does this mean? Where I'm from (Denmark) a fire alarm is...
  2. R

    Where in orbit should a rocket fire to escape with minimum ΔV

    I am really lost on how to deal with this. Since this is an elliptic orbit, the mechanical energy is negative. For the rocket to escape orbit, we have to get the mechanical energy to be equal to or greater than zero. I thought at first that it would escape in the perigee, since that's where the...
  3. phinds

    Who Was the Legendary Great Ball of Fire in Rock and Roll History?

    Along w/ Elvis, Buddy Holly, Little Richard, and many other founders of rock and roll, Jerry Lee Lewis really was a great ball of fire. https://www.cnn.com/2022/10/28/entertainment/jerry-lee-lewis-dead/index.html
  4. phinds

    Video card in my workstation only shows background on fire TV

    I just got my first fire TV and in HDMI1 mode (show computer video) it only shows the background of what shows on the monitor. My previous TV with a firestick showed everything although I never did get the sound to work through the HDMI cable. In the NVIDIA control panel, it shows the fire tv...
  5. J3J33J333

    I Can you put out a fuse (fire) with a laser?

    I was wondering you if you could use a laser to put out a fuse or to stop combustion? Could you use some form of laser/laser cooling to put out an explosion mid-explosion?
  6. MevsEinstein

    B Predicting the movement of fire

    I was staring at this barbecue fire. While my family was enjoying the heat, I was wondering why the flames all of a sudden shrink and then resize, and also take different shapes. Is there a way to predict this movement? Just curious :smile:
  7. A

    Engineering Systems Engineering QFD on an Aerial Fire Fighting Aircraft

    Hi everyone, I am currently taking an aerospace systems engineering course and right now, the focus is on Quality Function Deployment (QFD), which is basically a method driven by customer requirements, which can capture customer requirements and systematically convert them into engineering...
  8. A

    How long before this type of metal roof will melt in a house fire?

    Given a gauge 25 (0.02" or 0.5mm) metal roof roll formed made from hot-dip galvanized cold rolled mild steel. How long can these thin metal roof melt in a typical house or office fire with typical fire load? I read conflicting information. Some roof contractor said these thin gauge 25 metal...
  9. nsaspook

    Vangelis: Composer of Blade Runner & Chariots of Fire Passes Away

    https://www.avclub.com/rip-vangelis-blade-runner-chariots-of-fire-1848950743 R.I.P. Vangelis, legendary composer behind Blade Runner and Chariots Of Fire One of film’s most iconic composers has died, with Variety reporting that Vangelis—a.k.a. Evángelos Odysséas Papathanassíou—died on Tuesday in...
  10. Greg Bernhardt

    Ukraine nuclear power plant Zaporizhzhia on fire

    Let's keep this non-political, similar to the Fukushima thread. Thanks! https://finance.yahoo.com/news/1-ukraine-nuclear-power-plant-001225198.html
  11. Wrichik Basu

    Changing proxy server for WiFi in Amazon Echo Dot and Fire TV Stick

    One of my relatives has an Amazon Echo Dot and a Fire TV Stick. Both are connected to the same WiFi. Recently, their internet provider changed the proxy settings such that the default proxy no longer works. They have provided a set of proxies that can be used instead. We have manually set those...
  12. M

    Temperature vs moisture content to sustain a fire in a given material?

    So I've been trying to start a fire in which was successful for 10 minutes then died down due to high moisture in the leaves and branches. Which made me think of this phenomenon. is there a graph relationship to burning an organic, non-metal material that is well defined in relation to the...
  13. C

    Fire protection -- Water in a cylinder pressurized with Nitrogen

    I wondered if anyone could help, I work in the fire protection industry. We currently have a project using a pressurised cylinder. The cylinder hold 200 lites of water plus 40 litres of nitrogen gas as a propellant at 10.0 bar. I’m trying to work out once the 200 litre water volume has been...
  14. A

    Thermodynamics of a Fire Resistant Safe

    Hi, I have been researching how to protect my card collection from the unlikely event of a house fire, however there is not enough data for me to estimate whether my set up is adequate or not. If anyone could approximate anything here without knowing all the exact variables (r-values) that...
  15. BillTre

    Holiday Farm Fire: Terrain's Impact on its Spread

    This article (open access I believe) from the local newspaper (The Register-Guard) has several aerial pictures of the landscape, in areas burned by the Holiday Farm Fire (~30 miles from Eugene, where I live). It shows a patchy distribution of burned areas. This is probably good, in that...
  16. M

    A Solution to an ODE (Leaky Integrate and Fire Neuron Model)

    I'm looking for a general analytical solution to a particular ODE that comes up in neuroscience a lot. My feeling is that such a solution can't be obtained, otherwise someone would have presented it by now, but I don't have a good understanding of why it is so hard to solve. The equations as...
  17. M

    Fully analytical solution for the "Leaky Integrate and Fire" Neuron model

    Does anyone know if it is possible to develop a fully analytical solution for a leaky integrate and fire neuron driven by arbitrary time-varying current? Here's what I have so far (setting as many possible constants to 0 and 1): The equations: ## \dot{V} = - V + I(t) ## and if ##V(t) = 1##...
  18. Y

    Does creating fire break lines work to control forest fires?

    I really don't want to get into politics, I am sick and tired of smelling and breathing the smoke from the forest fire in N Calif even I am living in the silicon valley. Trump said because Calif refuse to clear fire break lines, clear the debriefs, then once the fire started, there is no break...
  19. S

    Construction "Class" fire ratings vs hour fire ratings

    Do (USA) fire ratings for wall coverings (Class A,B,C) relate to fire ratings given in hours for materials like drywall? I'm particularly interested in how ornamental ceiling tiles that have a "class A" fire rating ( e.g. https://www.amazon.com/dp/B00319FP8Y/?tag=pfamazon01-20 ) affect the fire...
  20. WWJR

    B Can a Fire Tornado Flip an 8 Ton Truck?

    Posting from over here in Australia, we've been going through some nasty bushfires and on the news I saw a report of a fire truck that had a full tank of water get flipped on its side and resulting in one fire fighter losing his life - apparently a fire tornado flipped the truck. My question...
  21. F

    Mounting fire / smoke alarms with magnets

    I am building a detachable smoke detector that I'm planning to install with magnets. I am concerned about the safety using this method, because of my knowledge of how magnets react to / affect heat and smoke. I wouldn't risk having the alarm detach itself during a fire, or the magnet to...
  22. pnstu

    Determine when (m), and how long the rocket should fire.

    Homework Statement: Your job is to determine when the lunar lander should fire its rocket to reduce its landing speed to below 5m/s for a safe landing. The lander will descend to the moon from an orbit 1000 meters above the surface of the moon (acceleration = 1.625 m/s^2). To avoid crashing...
  23. Wrichik Basu

    Automotive Car on Fire - Causes and Possible Methods of Prevention

    This is a picture that was published today in our local paper: This is not the first time a car has gone up in flames. A number of cases have been reported where cars moving on roads have, all of a sudden, blazed up. In a significant number of such cases, the people inside breathed their last...
  24. Greg Bernhardt

    News Massive Fire at Notre Dame cathedral

    Wow this is crazy. What a beautiful and historic building. Some images look like it could be a total loss. https://www.cnn.com/world/live-news/notre-dame-fire/index.html
  25. J

    Electrical Heating Pad Failure Build Your Own How Not To Start A Fire

    I have a little heating pad 12" X 15" runs on AC 120 volt has around 220 ohms resistance on low final got to hot burned up wire. What to replace it with using junk box parts light bulb wastes 10% for light would need metal cage to keep bulb from breaking seems like not good way. Have 300...
  26. T

    Maximum height for water from a fire hose

    Homework Statement Fire hose has diameter of 4.0 cm and flow rate of 10 L/s. There is pressure of 2.2 bar inside the hose. How high the water can go at best? Water density is 1.00E3 kg/m^3 and air pressure outside the hose is 1.0 bar. Homework Equations Flow rate $$ Q = Av $$ Newtons...
  27. L

    How to get Kindle Fire 7 on the internet

    I just got my Kindle, I'm able to connect to the wifi easily, but whenever I try to get on the internet with it, nothing loads. Everything tells me I have no connection. When I connect to the same wifi with my phone, the internet works just fine. I've contacted both Amazon and my internet...
  28. nsaspook

    Is It Possible to Replace Elon Musk as CEO of Tesla?

    I'm pretty sure a company like Tesla could crater without him as the intellectual explorer and inspiration but 60% of TSLA's ownership is Institutional Investors. I would not be happy with the stock today...
  29. gleem

    News Brazil's National Museum is Destroyed in a Fire

    Yesterday Brazil's National Museum 's contents where destroyed, artifacts of.Brazil's history gone. https://www.theguardian.com/world/2018/sep/03/fire-engulfs-brazil-national-museum-rio Apparently the government was lax in maintaining and upgrading the structure. It is hard to imagine...
  30. V

    How can California's timber industry help reduce the risk of wildfires?

    I been keeping an eye out on the recent fires we are experiencing around the California, Oregon, Washington and in the Idaho areas. It seems like as years go by fire season is getting worse. What really spooks me is that the drought areas are spreading to larger regions and impacting wild...
  31. D

    Skyscraper's Fire Supression System

    https://www.imdb.com/title/tt5758778/ In Dwayne Johnson latest movie Skyscraper.. is the fire suppression system that can immediately put out fires based on a real technology? For 100 stories building.. what kind of fire suppression system do they use? A fire in any floor (say the 40th...
  32. M

    Difference between flash point, fire point and self ignition temperatures

    Is there any difference between setting petrol on fire directly(by contacting it with burning stick) and heating petrol in a vessel, increasing its temperature above itself ignition temperature and making it burn spontaneously? What is the difference between flash point,fire point and self...
  33. A

    B Exploring the Conductivity of Fire: Debunking Common Misconceptions

    Hi Why is fire conductive? Have encountered several examples where fire is used as a conductive material in high voltage demonstrations. However I've never gotten a straight answer as to why. Some sources claim fire is a plasma, but that's not true. The flame of a candle is not hot enough to...
  34. D

    At what temperature does paper catch fire?

    If there is a paper glued to cctv camera that is hot (continuous operation)... can the paper just combust? what temperature can it do that?
  35. T

    I Equation for Fire Evolution Dynamics

    It is NOT about the heat equation. I'm asking about a dynamical system or equations set to describe fire evolution, with given fuctions of air, material and enviorment change.
  36. T

    Residual pressure in a fire sprinkler system

    I'm aware that the term means the remaining pressure at a point while there is flow. Say the distribution pipes downstream the sprinkler valve have a calculated total head loss of 3 bars during the designed flow. Does that mean that the residual pressure at the sprinkler valve needs to be at...
  37. T

    Pressure Drop in a fire fighting network with loops

    Hello Everyone, Can someone please explain to me how I would go about verifying the External Static Pressure of a pump that feeds a pressurized fire fighting network with loops in it. An image of the network is attached. I'm not being able to grasp the concept of pressure drop in a pressurized...
  38. Q

    How light rays from a fireplace wood fire on Earth compare to the Sun's fire?

    While lying in front of a 500 degree woodfire, I wonder if besides light and heat that we take as ordinary does it also have ultraviolet rays of light like the sun?? What are the types from light from an ordinary on Earth fire?? Would they be beneficial to plants as main light source?, would...
  39. M

    Can People Catch Fire Naturally?

    I would like to ask you whether or not people can caught fire naturally. I remember there was a discussion in the tv but I cannot google it because I don't know correct terms. Source: Self-made Thank you.
  40. A

    Does anyone know of a thermally-stable endothermic reaction?

    Hello all, I've used physicsforums a few times over the years, but I believe this is my first post. I'm working on an engineering project in which I need to find a highly-endothermic reaction where the reactants and products will be stable at very high temperatures (well over 800C), or at least...
  41. R

    I Processes that determine the color of fire

    I never really had a good idea of the mechanisms behind color. why we feel heat, what determines the color of fire, etc. So, today I sat down and did some research. I want to explain the processes here to make sure I got it completely right: For complete combustion of most hydrocarbons (blue...
  42. T

    Exhaust velocity of a fire extinguisher

    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > Hey, For our project we have to think of an experiment that can kind of simulate a rocket. We decided to use a fire extinguisher on a kart, since its mass constantly changes (same with a rocket)...
  43. Y

    Fire Hose Power Output, Given Height and Radius of Hose

    Homework Statement A fire hose for use in urban areas must be able to shoot a stream of water to a maximum height of 34 m. The water leaves the hose at ground level in a circular stream 4.0 cm in diameter. What minimum power is required to create such a stream of water? Every cubic meter of...
  44. R

    B Understanding Black Body Radiation and the Sun's Color Temperature

    So, if frequency(max) of light emitted from an object proportional to temperature in kelvin, how can sun have max frequency around the yellow region while blue flames are much less hot?
  45. T

    Fire sprinklers - residential vs. quick response

    I never really understood the difference between these two. I believe I've heard someone say that all residential sprinklers are quick respons sprinklers, but not all quick respons sprinklers are residential sprinklers. Is that accurate? Even if it is I still don't get what differs the two...
  46. Delta Force

    March 1945 Hanford Substation Fire

    To clarify why I'm asking this, I'm interested in counterfactual history and this is a little known event in early nuclear history that could have had major repercussions for the Manhattan Project and the end of World War II. On March 10, 1945, one of the last Japanese fire balloons fell on...
  47. C

    How Can Bernoulli's Principle be Related to Fire Hoses

    Hello everybody: I am trying to test, using Bernoulli's Principle, when firehoses are most effective. I know this is extremely broad, but does anyone have any ideas for independent variables? I am thinking about the the width of the end piece of the nozzle... Any help/guidance would be...
  48. G

    Fire an arrow at a moose as it runs away

    http://imgur.com/a/FKkHL 1. Homework Statement A moose is running away at 25m/s. You fire an arrow at 30 degrees when it's 120m away. What must the velocity of the arrow be in order to hit it? Homework EquationsThe Attempt at a Solution Please see attached picture, I'd type it out but I'm...
  49. I

    What influences ignition temperature and oxygen consumption

    Hello, This is for my independent game development project. I am aiming to simulate simple environmental properties in grid-based world. I have world made of cells (or blocks) and I consider each physical property to be constant and uniform in given cell. Some properties spread from a cell to...