Why are binoculars filled with nitrogen gas?


why are binoculars filled with nitrogen gas?

Sometimes we come across binoculars with some extra specifications such as “filled in with nitrogen or purged with nitrogen gas”. Most of them are. But why?

Why are binoculars filled with nitrogen gas? Nitrogen is usually purged into binoculars before the assembly of parts in order to remove all the impurities and the moisture in the best possible way and to prevent any condensation to be formed inside the binoculars, making them good to use under extreme weather conditions.

It is relatively common to find binoculars purged with nitrogen gas on an average price even some of the low-end budget may be filled with the nitrogen gas. You often may come across those binoculars to be waterproof, weatherproof and specifically fog-proof.

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Why are binoculars filled with nitrogen gas?

If you have or tried some of the old-class binoculars which belonged to your grandparents from the WWII or any of the classic ones which in that time, the binoculars were not nitrogen purged, you may have noticed inside of them the mould or fungus ruining the quality of the binoculars.

It is true, indeed, that the mould and fungus under right conditions are forming inside the binoculars. And those conditions are a high level of humidity and warm temperature. But it is not about the storage, it is about the fact that some of the old-class binoculars are forming condensation inside in special when you are using them under a difference of temperature (from indoors to the freezing cold outdoors). And that condensation leads to the forming of fungus or rusting if the binoculars are metallic.

The nitrogen-purged binoculars are often sealed with an O-ring seal which prevents the gas to go out of the binoculars and an optimum pressure to remain inside.

Let’s have a look over all the advantages of having nitrogen-purged binoculars.

  • Removes all the impurities before assembly the binoculars, therefore, no dust or any other impurities will be even inside the binoculars
  • Also removes and prevent the forming of condensation inside the binoculars.
  • Good for the long-time run to avoid the binoculars of forming fungus, mould or rust inside.
  • Makes the binoculars weatherproof and to be used under extreme weather conditions, incl. cold, humid or freezing places.
  • Also makes the binoculars waterproof and fog-proof. Fog is a high level of humidity, therefore, no condensation will be formed inside the binoculars.
  • Maintain the high-quality of the optics in time.

Now, this does not mean that you have to be careless of your binoculars if they are nitrogen-purged. Think about the fact that the esthetics of the binoculars may matter and the outer glass can be also damaged or the quality to decrease in time, in special if they are misused.

Nitrogen or non-nitrogen binoculars?

It is a rhetoric answer. Definitely nitrogen-purged binoculars. For the above specific reasons, of course. Nowadays, it is a common thing to see on the market binoculars purged with nitrogen, where in the past this was not really possible.

The non-nitrogen purged binoculars are at high risk of degrading the quality in time and it is hard for them to be used in any extreme weather conditions, to be waterproof or to avoid condensation to be formed inside.

How to prevent condensation for non-nitrogen purged binoculars?

It may be a bit difficult and one another headache to ensure the extra protection for the non-nitrogen purged binoculars in the long-run but first and the most important key point is to ensure that you store them into a dry place and avoid using them in cold and humid environment in special in foggy weather.

Also, it does make sense not to use them during the rainy day even if the binoculars may be waterproof which is hard to believe. Therefore, avoid anything to do with humidity.

Alternatives to the nitrogen-purged binoculars?

There are alternatives to the nitrogen-purged binoculars such as argon-purged. There may be other gases too which will have the same aim – to keep the binoculars moisture & dust-free, but it is not that common to find other gases purged into binoculars rather than the nitrogen. I am not aware why is the nitrogen used over any other gases but it may have a connection with the maintaining quality on the long-term run, better job at protecting and the manufacturing prices are lower.

How are the binoculars filled with nitrogen?

During manufacturing and before assembly the last parts into the binoculars, they are purged with nitrogen gas at high pressure. By doing this in the first place removes all the impurities and the condensation from before assembly and making the binoculars oxygen-free. The valve now will have the role to keep the pressurised nitrogen inside.

Are they safe to use? Is it something to worry about?

Yes, the nitrogen-purged binoculars are very safe to use and there is nothing to worry about even if in the nearly-impossible circumstances where the nitrogen may leak due to damaging to the binoculars, do not worry, this is not lethal. The worst part would be that oxygen will get back inside the binoculars making them vulnerable to condensation and forming of fungus in time.

If your binoculars need repairs, I strongly recommend to take them or send to a specialized centre and not try to repair by yourself. Just ask yourself one question: how are you able to refill the inside of the binoculars with nitrogen if you are going to fix by yourself.

But as a general query and research, even in case of a leak if you are not going to inhale directly the nitrogen gas as you do with a helium balloon, you should be just fine. The nitrogen will quickly disperse into the atmosphere.

Where and how can I use the nitrogen-purged binoculars?

This is a big question and my answer for that is everywhere where a normal pair of binoculars may not be usable, such as extreme weather conditions – rain, storms, snow, ice, foggy weather, desert and so on.

Wherever a normal pair of binoculars will not only have a hard-time of proper function under the above circumstances of usage, nitrogen-purged gas binoculars will do just fine, even underwater. Just don’t do as I’ve done to panic whenever I took my binoculars from the cold-outdoors to the hot-indoors and the condensation started to happen on my binocular lenses – This will definitely happen but only on the outer part of the glass and not inside the binoculars.

If you are an outdoorist, nature lover or birdwatcher, the usage of binoculars may involve some uncertain weather conditions. Nitrogen-purged binoculars will do just fine under any of the above-mentioned weather conditions and even more. Please check our binoculars buying guide for more information.

The final conclusion

If you are buying your first or a new pair of binoculars, this is not the absolute main factor to look over, if your binoculars are going to be nitrogen-purged or not. Always consider the magnification and the objective lens diameter over this factor. But nowadays, if you are going to invest in a good pair of binoculars, most of them are going to be nitrogen-gas purged.

Therefore, it is a good practice to make sure that your next pair of binoculars are going to be gas-purged to ensure the usability under any weather conditions. You may often come across spotting scopes and even telescopes with the same structure where they are purged with gas to remove all the impurities and the moisture and to ensure the best experience when using a pair of binoculars.


Thank you for sticking until the end of the post, if you have any question you can ask in the comment section below and I will try my best to answer you in the quickest way possible. For now, farewell and take care. Do not forget to give us a share to spread the love of binoculars 🙂

Gabriel Mihalcea

Passionate about binoculars, photography and blogging with years experience behind, I love to split my time and observe the beauty of this world with different eyes.

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