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The atmosphere of Earth, commonly known as air, is the layer of gases retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).
By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.
Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere.Earth's early atmosphere consisted of gases in the solar nebula, primarily hydrogen. The atmosphere changed significantly over time, affected by many factors such as volcanism, life, and weathering. Recently, human activity has also contributed to atmospheric changes, such as global warming, ozone depletion and acid deposition.
The atmosphere has a mass of about 5.15×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km (62 mi) or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.
The study of Earth's atmosphere and its processes is called atmospheric science (aerology), and includes multiple subfields, such as climatology and atmospheric physics. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The study of historic atmosphere is called paleoclimatology.

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  1. A

    Samsung Air Source Heat Pump

    My ASHP has been set to 55 degrees C for the legionella in the control panel but I thought it had to be set to 60. Engineer seemed to think this is ok. I note that in 6 weeks I have had error E919 which is telling me the unit couldn't perform the correct heat for legionella thus the error code...
  2. J

    Air admittance valve below toilet

    Hi, I am installing a new en-suite toilet upstairs in a new location , the soil stack is installed by my builder going downstairs directly and into the ground where the main sewers are. He’s installed the air admittance valve on the floor below , which is slightly below where the toilet is...
  3. K

    Air to Air heat pump

    Has anyone installed / worked with air-to-air heat pumps? I wonder if their running cost is also high? There’s no information on running cost and even the people handling the funding pots for Air source heat pumps, are not aware of the costing.
  4. D

    How do I bleed a boiler with air in it?

    Hi I have drained my system to install a magnet filter on the boiler inlet and put some x400 into the system to leave for a few weeks to combat some growing sludge. After draining it and then refilling and bleeding the radiator floor by floor from the top floor down the boiler has air in it...
  5. J

    Problems with air entering central heating system

    Air entering central heating system and hot water pumping over into make up tank in artic when h/c control is switched on. There is no problem when only c/h is on! this situation as only occurred since replacing my Grundfos UPS2 with a UPS3 I have tried the pump on different speeds . On the box...
  6. J

    Air in central stem when hot water is switched on

    Replaced Grundfos Ups 2 C/H pump with a Ups3. when c/h only on no problem as soon as h/w is on as well gurgling and air in system experienced, also hot water coming out of 22mm vent into expansion tank ( doesn't happen when only c/h is on) so bad that h/w must be turn off. I had no problem...
  7. G

    New Eco 7 Cylinder - spluttering/air in system?

    We've just had a new Economy 7 cylinder put in and after 3 or 4 days we still seems to get spluttering out of the taps as thought there is air in the system Basic setup as follows - apologies for poor terminology as i'm not a plumber! Cold water tank in loft of bungalow feeds into the hot water...
  8. S

    Is this an air separator?

    Hello, I have been sent this and they said it’s leaking near the top. Am I right in thinking this is an air separator and the top is leading up to the vent pipe of F&E tank? All the ones they seem to sell look totally different. Thanks
  9. T

    Air admittance valve

    Hello, DIY plumber here, I’m after some advice regarding an AAV, my current one goes though the loft and the roof with a vent on, iv seen on some pan connectors have 32mm air admittance valves built on to them. Does this mean I don’t need the 110mm pipe into the loft at all? TIA Tom
  10. S

    Air in towel radiator

    Our upstairs towel radiator keeps filling with air at the top. We had a new system boiler, new tank and new pipework fitted in October. The new tank is in the garage which is underneath the house and the new boiler is in the kitchen at ground floor level. We also had underfloor heating installed...
  11. S

    Air in towel radiators

    Air keeps collecting in our upstairs bathroom towel radiator. Do we have a leak or what could be the cause please? We had a new system boiler and tank installed and all new pipework. The 3 towel radiators are on a separate system to the radiators in the other rooms. The tank is in the garage...
  12. M

    Do I need an air admittance valve

    Hi everyone,, I'm a keen DIYer and need some advice on AAV or durgo valve,, we're renovating our house and plan to put a bathroom on the other side of the house, we currently have an old stack going straight up through the roof which is open to vent naturally, we plan on putting another soil...
  13. A

    No air or water - noisy radiator

    Hi, hoping for some advice with radiators that I don't seem to be able to bleed. This is my second winter in a new build. The towel rail was making a knocking/pinging noise last winter so when I recently had my boiler serviced the engineer adjusted some screws on the rail itself and it's...
  14. P

    What external Air admittance valve would you recommend?

    Hi I want to fit an external air admittance valve to a new stack pipe, see picture. Does anyone have a particular recommendation. Many thanks Paul
  15. R

    B11 air intake filter

    Where can I get either a new sponge filter or complete cover that sits over the impeller fan the rubber filter has perished, or is it an acoustic barrier, either way its gone
  16. nick_a_louse

    Air getting into upstairs radiators. Possibly caused by kettling?

    I need some help from the internet before I waste any more time and money trying to fix air getting in to my central heating! Looking for advise on what to do next, as the 3 plumbers I've used so far haven't been much use. Down in East London, near Romford for what it's worth! Issue summary...
  17. S

    Central Heating Air Build Up and Cylinder popping noises

    Hi Guys, Been having a real saga and head scratching situation. I originally had 1 problem, and now 2. Original issue: Air being built up in rads. Having to bleed every other day if not daily. All upstairs rads getting air, and one downstairs in utility room, same room as boiler and not far...
  18. V

    Repeated Air in Central Heating System - Help appreciated

    Hi, I'm hoping for some suggestions as to where I go next in my endless mission to stop my system taking on air. The house has a gravity fed system, 'S' plan, Heat only boiler supplying CH & HW, with separate F&E and vent just before the pump in the typical H layout, pump & valves are all...
  19. S

    Megaflo air bubble regen frequency.

    Hi guys was wondering if anyone can advise on the frequency of having to recharge a megaflo air bubble? I have had mine installed not for 6 months and noticed the turndish was dripping, so I shut the cold feed off, let the pressure off and regened the air bubble. This seems to have sorted the...
  20. 2

    Advice on air admittance valve. Toilet

    Please see pic! I can't seem to fit this air admittance valve on the back of the toilet. Is there any other fitting I need for this to work.