Nitrogen Tyre Inflation

REASONS WE DO NOT RECOMMEND IT

There are no discernable benefits for ordinary road cars

After researching many web pages and sources about using Nitrogen to inflate car tyres I summarise the information I have found here.
Car tyres are normally inflated with compressed air.
Air is approximately 80% Nitrogen, 20% Oxygen.
Nitrogen is comparatively inert, Oxygen is a reactive gas.
The Nitrogen used for inflation in tyre depots is normally generated by a separation process from compressed air. It still contains about 5% Oxygen.
Nitrogen used at race tracks and in industry may be 99%+ pure and contained in high pressure cylinders at 2000+ psi.
Both sources of Nitrogen will be treated to reduce the amount of water vapour.

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Claims	Answers	Explanation
Nitrogen filled tyres hold their pressure for longer than normal air	WRONG (as far as tubeless car tyres are concerned)	Research Data from Dupont shows that although Oxygen is the heavier element it does leak through a porous rubber membrane faster than Nitrogen, but the rate for both gases or a mixture within a tubeless rubber tyre which has an IMPERVIOUS liner is so slow that it would take SEVERAL YEARS for all the oxygen in an air filled tyre in good condition to leak away: though greater leaks can occur around the rim-to-bead seat - so the answer here is to ensure the tyre is properly fitted and sealed. Many tyres used in the earthmoving and mining industries still use tubes in which case the leakage data and benefits of Nitrogen may be more relevant.
The inner lining of the tyre and the wheel do not become oxidised or corroded or perish if filled with Nitrogen	WRONG (as far as tubeless car tyres are concerned)	Given the average life span of a normal car tyre is 2 to 5 years, depending on use, and the average life of a vehicle is 10 to 15 years, the amount of corrosion of the wheel or degradation of the inner tyre lining from the oxygen in the air is not measurable. The only time significant attack to the wheel is likely is if the air in it has a very high water content to assist the oxygen in attacking the wheel. In 15+ years of fitting tyres I have never seen a wheel or tyre that has suffered in such a way: but the exposed outer part of the tyre or the external edge rim-to-bead seat may often show degradration. The only advantage of Nitrogen is that it would be dried to remove any surplus water vapour. Some tyres used in big earth moving equipment are filled with Nitrogen but these tyres are very heavily constructed and so may be remoulded several times in their life span over several years: therefore anything which helps to keep the tyre carcass in good condition is worthwhile given that the tyres can cost several thousand pounds each, and are inflated to much higher pressures than passenger car tyres.
Nitrogen is more stable at holding it's pressure when the tyre goes through the cycle of cold to hot and back again in normal use.	WRONG	Oxygen and Nitrogen and Air all respond in the same way to temperature changes as the tyre heats up and cools down: they all have the same rate of pressure change for an equal amount of temperature change. Again the only exception would be if very wet air was used to fill the tyre: if the water content was so high that in cold temperatures there was liquid water in the tyre which could turn to water vapour when the tyre heated up. This would cause an uneven pressure gradient in respect of temperature: effectively a very small amount of water would turn into a large amount of steam within the tyre casing. In normal use (at least in my tyre depots) the air-lines are fitted with water traps to remove excess moisture from the compressed air.
Nitrogen is not a fire risk	CORRECT	It is a requirement to use Nitrogen (or another inert gas) with less than 5% Oxygen content for aircraft tyres. For aircraft where the tyres in normal flying use are stowed within the wings or fuselage it is obviously desireable to have a tyre NOT filled with pressurised air should a fire occur. The amount of water vapour and carbon dioxide in the tyre should also be minimal or it could condense at high altitude and freeze to ice which would give an unbalanced situation when landing. The fire risk benefits of inert gas filling also apply in other safety critical situations, but have no real advantage for private motoring.
Nitrogen is used in Formula 1 and other race cars.	CORRECT	Nitrogen is used because it is easier and more reliable than using an air compressor. The cylinders of Nitrogen are also used to power the impact wrenches for wheel changing.
Car manufacturers still use compressed air when making new cars	CORRECT	See the reference to Vauxhall cars. They do not disapprove of Nitrogen but do not seriously endorse any of the claimed benefits. Link to Vauxhall Advice

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Nitrogen is a dangerous gas

I have copied the text below from a post on the Lexus Owners web site

Everybody has seen the warning signs for the risks of nitrogen. Nitrogen is dangerous because it actively pushes away the oxygen in the surrounding air. But what actually happens if you do not get enough oxygen? In order to understand this, it is important to know a little about the human breathing system.

How does our breathing system work?

Humans need oxygen in order to be able to live. Our body uses oxygen to supply energy to our organs. The oxygen is burning sugars in the body cells, supplying energy to our body. The waste product of this energy burning process is Carbon Dioxide.

In order to get Oxygen into our bodies we inhale fresh air. Fresh air contains on average, 21% of oxygen. Inside the lungs, the oxygen is connected to the blood using the red blood cells. At the same time, the Carbon Dioxide from the blood is released to the lungs. When we exhale we blow this Carbon Dioxide out of our bodies. Inside the body we produce as much Carbon Dioxide as we use Oxygen. If we start working harder, we need more energy; therefore we start burning more sugar. This causes the frequency of our breathing to increase, for we do also need more Oxygen for this process. The result of this is more Carbon Dioxide. The fact that 79% of the air we use is typically Nitrogen is not important. It dissolves a little in our blood, but it is not connected to the blood cells.

The frequency of our breathing is automatically controlled in a part of our brain, which we can call the Breathing Centre. If you think this breathing centre is triggered by the amount of oxygen in the blood, you are wrong! The breathing centre responds to the amount of carbon dioxide present. The more carbon dioxide that is detected by the brain, the faster we start breathing. This process always works well because we produce the same amount of carbon dioxide as we do use oxygen. This way, we never get a shortage of oxygen. This process never fails, even when we are asleep, or inside a sealed conference room with a lot of other people, which would cause the carbon dioxide levels in the room to increase rapidly and the oxygen levels to decrease. Our bodies would respond to this by breathing faster in order to get more oxygen into the lungs. Getting the feeling that you are short of breath is a signal that will finally cause us to leave the room if the carbon dioxide levels continue to rise.

When we inhale Nitrogen, why do we die so quickly?

Humans are the most resilient species on the face of the earth. We can exist in the most diverse of circumstances and environments. That is until we are confronted with circumstances not foreseen by nature itself; an environment that contains a lot of nitrogen. What is so different? Suppose we inhale air with only 10% of oxygen, no carbon dioxide and 90% nitrogen. We inhale normally and use the oxygen for our energy production. Because there is insufficient oxygen in this air, we shall suffer a shortage of energy because of the lack of carbon dioxide. Therefore the brain is not stimulated to increase the frequency of our breathing. In fact, the brain is stimulated to decrease the frequency of our breathing because the amount of carbon dioxide in our blood is reduced. Because of the acute need for oxygen, the energy supply to the cells will stop, which in basic terms, means "lights-out". The brain is extremely sensitive to this power failure and will not be able to maintain consciousness.

Being unconscious, your breathing will be very slow. If the oxygen level falls below 6%, this will take place after just ONE BREATH of air. You will quite literally faint after inhaling and will no longer to be able to breathe by yourself. After about 2 to 4 minutes, you will die. Within this time, only mouth-to-mouth resuscitation could save your life. The exhaled air of the rescue worker contains a lot of carbon dioxide that should stimulate the brain to start breathing again.

Nitrogen is the most dangerous gas that we know. Even the most toxic of gases will give at least a small warning to the body. Nitrogen does not. Because of this lack of warning we cannot protect ourselves from it. A few lucky survivors (resuscitated) of nitrogen accidents in the industry have all declared that they never knew what hit them when they were exposed to high concentrations of nitrogen.

So how can I protect myself from high concentrations of nitrogen?

Take a gas sample. Calibrated equipment that is being operated by trained personnel can determine if it is safe in a certain area or confined space.

Always use breathing air (cylinders) in nitrogen rich environments. Canister masks will give absolutely no protection from oxygen deficiency.

Stay away from nitrogen leaks, manholes and other openings of vessels and towers.

Never use nitrogen hoses to blow something dry or clean unless you are using BA.

Never check a confined space by holding your breath for a second and putting your head in. The penalty for this is death, for even the smallest mistake.

If you purge a system with nitrogen make sure that all warning signs, warning tapes etc are in place so that everyone in the area is made aware of the hazards. Only then you may start your work.

Never, on no account, must you ignore a warning sign or fence.

Never try to rescue a victim of nitrogen with using BA yourself. A rescue without BA will result in double the amount of deaths.

Always be aware of the hazards of nitrogen.

HOPE THIS CLEARS THINGS UP A LITTLE