How Do Welding Helmets Work? [Passive v Auto Darkening]

Welding helmets use a lens to protect your eyes from UV and IR light. Passive helmets use lenses which are changed manually, while auto-darkening helmets automatically adjust the darkness for you.

As well as protecting your eyes, welding helmets also protect you in other ways.

  • Welding temperatures are very high, and if your face is in close proximity, it could burn. A welding helmet will shield your face and eyes from these high temperatures.
  • Spatter is another consideration. This can burn your face, eyes and skin, so a helmet is essential for protecting your face from spatter.
  • Welding can create fumes and helmets can help to keep some of the fumes at bay.

If you know you are safely protected, you can concentrate on the job in hand.

Types of Welding Helmet

There are different types of welding helmet.

  • Fixed-shade

As the name suggests, these have a fixed lens. This cannot be changed and usually has a shade level of 10. If you only work on one type of project, or carry out your own DIY, then this would be a good choice.

  • Passive

Passive welding helmets cover the face, and use changeable lenses to alter the darkness. They are made from high quality glass which is coated to provide you with protection from UV and IR.

As the lens is changed manually, you will need to know which one to use for each weld, to make sure you have the right protection. You will also have to stop working if you need to change the lens over.

They are the cheaper option, and the lenses are cheaper to replace.

  • Auto-darkening

These are the more expensive option, but they do a lot of the work for you.

They are also made from quality glass and provide protection from UV and IR. The main difference is that the lens will adjust the darkness automatically, as soon as it detects a spark. You don’t need to stop to change it each time.

Auto-darkening helmets are available as:

  • Solar-powered. These use a fixed battery which cannot be replaced, and is charged using solar power.
  • Battery powered. These use replaceable or rechargeable lithium batteries.

The fact that they use batteries means they do have a limited life and will eventually need to be replaced.

Auto-darkening v Passive

  Passive Auto-darkening
Cost The cheaper option More expensive
Lenses You have to stop work to change the lens Will alter the darkness of the lens automatically when it detects a spark
Power Need no power to operate Use solar power or batteries. This means they will eventually need to be replaced
Added protection May not protect you against an accidental spark Will react immediately to any accidental spark
Experience You will need to know which lens to use for which welding job You need limited knowledge, as the helmet detects the darkness automatically

Making Sure Your Helmet Works

If you weld regularly, then you will know when your helmet shows signs of needing to be replaced. If you don’t then you should always check before you start welding.

One of the tell-tale signs is eyestrain. This is an indication that the lenses may not be working as efficiently as they should be.

There are a couple of simple tests you can do to check if the lenses are working as they should.

  • Light a torch and make some sparks. If you have an auto-darkening helmet, then it should switch to dark mode.
  • A simpler method is to look at the sun. A passive helmet should provide adequate shading and an auto-darkening helmet should switch to dark.
  • If you have an auto-darkening helmet you may also need to keep an eye on the reaction speed. The usual standard is 1/2500ths. If you create sparks and it doesn’t switch immediately, you will be getting some of the effects of the flash, so this will need to be looked at.

Frequently Asked Questions:

How long do auto-darkening helmets last?

More expensive helmets will last longer, but if you use is regularly, this will also effect the life of the helmet. As an average, an auto-darkening helmet will last between 3-5 years.

How do I clean the lenses?

If the lenses get too dirty, it will affect your weld as you won’t be able to see. Use simple detergent with a sponge to clean off any excess dirt. Don’t use anything too abrasive or anything which will scratch the surface of the lens.

Why do I need to test my welding helmet?

If you’re helmet is not working efficiently, you risk damaging your eyes. If you don’t use it regularly, check it to make sure the batteries still work and that the lenses are still reacting to light. It’s best to check than come to use it and find it’s no good.


A welding helmet is an essential piece of equipment. It protects your eyes from harmful light, your mouth and nose from harmful fumes, and your face from heat and spatter. A helmet should be lightweight and fit neatly around the head. Too tight and it won’t lift up properly. Too loose and it will move around too much.

There is no best option for a helmet, so choose the one which best fits your welding needs and your budget. Look after it well, and it will protect you for many years to come.

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