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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. T

    Shower Pump on air to water Unvented Cylinder?

    Hi, I'm in my new build 2 years and the shower pump has died. I have an air to water unit downstairs is in the utility which I've been told is unvented and pressurised. The cold water feed into this cylinder is from the attic tank, not the mains as I turned off the mains stopcock to see if hot...
  2. D

    Frost protection valve, detect air or water temp?

    Hi, Short version: Do frost protection valves trigger when the water in the pipe gets to threshold, or when the air temp drops? Long version: I'd rather use frost protection + anti-freeze cycle on my mitsubishi ecodan heat pump. The warranty is apparently fine with that combination, and it...
  3. E

    Fitting an air admittance valve to 32mm push fit elbow problem

    In the photo there is a grey 32mm push fit elbow between the sink trap and down pipe. I want to replace the elbow with a "male" push fit tee attached to an air admittance valve to stop gurgling noises. I can't find a tee fitting that description, can anybody offer a solution as you can see space...
  4. F

    How dangerous is air testing pipework

    I've air tested pipework for years, typically 4 bar for 30 minutes. I've never had an issue with any pipework that has passed that test, occasionally you get a small leak from the air test typically old cap ends/scratched pipe which shows up easily on the test without having to inspect anything...
  5. G

    How to clear hot water air lock?

    I recently installed new hot and cold feeds to a new downstairs cloakroom. After refilling the system the hot taps were all dribbling, spluttering and showing signs of an air lock. I attached cold mains to a hot tap and left it running for 15 minutes, while opening up each hot tap. They all...
  6. I

    Automatic air vent leaking

    Dear professionals, could someone kindly advise on per below issue, please let me know if more pictures or details needed. I think my Auto Air Vent is now leaking. A little background on the boiler – installed a year ago in Feb, Valiant Heat only boiler Eco Tec plus 424, plus new pump. The leak...
  7. R

    Always lots of air in our CH system

    When I turn on our CH there's a lot of noise from one specific part of the system - the pipes on the landing, and one radiator. It sounds like air, and the landing radiator needs bleeding regularly (about once a month), even though it isn't the highest point in the system. The two upright rads...
  8. S

    Hot pulling air through open vent.

    Hi, I'm new to the forum and just some background on myself. I have 4 years experience as a plumber but haven't worked in the trade in 15 years. I would say my overall knowledge is not great as I did most of the 4 years working on rinse and repeat estates of houses. I was also quite young and...
  9. S

    Down-founded what to do

    Hey guys in the know. I have paid for a heating and plumbing contract and had to pay my excess 3 times for the same thing still not fixed. The issue is quite simple to repair not sure why any one of the 2 plumbers could not fix it. Why am I paying for cover. The auto air vents in part of the...
  10. P

    Grant Vortex 50/90 oil boiler with open air tube spigot

    Grant Vortex 50/90 condensing oil boiler where the air tube spigot over the fan is not connected to the existing flue, should this be closed off with a Reillo cover plate to stop vermin getting into the open fan motor.If is blanked over will need a further combustion test to confirm adequate...
  11. O

    venting question - using old empty outdoor SVP as air vent

    Hi all, I have an old toilet on the top floor (to be removed) which empties into an outdoor vertical SVP and into the ground. The pipe is straight with a vent terminal on top. Another toilet on the ground floor empties through the suspended timber floor into (what I suspect) a drain. I wish...
  12. O

    Recharging Air Gap on MegaFlo CL300

    Hi. I replaced the Pressure and Temperature relief valve on my MegaFlo CL300 (I had thought it was dripping but it turns out the overflow drip is coming from the 3bar safety relief valve for the red expansion vessel) Before I replaced the valve it would recharge the air bubble normally - the...
  13. Beyond the blue

    DIY air conditioning system

    DIY air conditioning system. I've got lots of plumbing experience and want to install my own a/c split system 3 to 1. I intend having it commissioned by an F Gas qualified company. When l tried to buy the system the supplier want all details of the F Gas registered 'installer' before releasing...
  14. D

    Wood burning stove with air to water heat pump

    Is it possible to install a wood burning stove with an air to water heat pump? I was speaking to a few plumbers who have said this is not possible as the air to water system is a pressurized system and the stove needs to be in a vented system.
  15. A

    Air trap after loft tank cleaning

    After cleaning up of loft big tank, water supply has stopped for taps due to bubble trap. How to release please?
  16. C

    Gravity Fed system in Bungalow with two Automatic Air Vents

    Hi, I’m replacing my old Honeywell Smartfit system on a oil fired gravity-fed system in a bungalow. I’ve read conflicting advice on gravity fed systems requiring an AAV, unless in a bungalow to aid bleeding on first fill? One AAV is in the loft on - what I think - is the boiler return pipe...
  17. M

    Sealed system grabbing air

    Any ideas why a sealed system with a combi could be grabbing air. The upstairs rads have air in and the system reads 3 bar cold. When the air is bleed out the system returns to 1 bar or less. It's an ideal instinct boiler basically a logic.
  18. L

    Megaflo auto air valve leaking again

    Hi, I noticed some months ago that my Megaflo auto air valve was leaking so I replaced it, the replacement valve has also started to leak with a waxy residue. I recall that the original AAV had a black lid and the replacement has a brass lid, does it matter which version is fitted? Can I...
  19. ameliacm

    Combined rain/sewage pipe hindering fresh air

    Hi there, Apologies for the mammoth post but my neighbours and I really need some advice... I recently purchased a flat that was built in 2016. The apartment is still under the NHBC 10yr warranty. Since moving in, I discovered that the rainwater pipe that runs through my winter garden balcony...
  20. M

    txn150pterp kingspan cylinder internal air bubble

    Has anyone worked to the txn150pterp kingspan unvented cylinders? They have an internal expansion bubble like the megaflows I believe. To repressurise the internal expansion bubble am I correct in saying turn the power off to the immersion/heating turn water off. Then open lowest tap to drain...
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