How do you choose the right welding hood? Well, first, let's talk about what's important about a welding hood. The welding hood is generally a plastic, non-flammable material with a protective screen behind which is the lens. The welding hood and its lens protect you from dangerous levels of UV radiation that are produced through arc welding.
Welding lenses come in a variety of shades from eight to fourteen, eight being the least dark, fourteen being the most dark. Ten is what you see most often sold in the welding shops. Some people like the lighter shades so they can see better. Other processes burn much hotter, such as Heliarc or TIG welding, and require a darker lens. All lenses, regardless of their shade, provide complete UV protection.
What you see here on the table are three styles of welding hood. This one is the most modern. The middle one is intermediate. And the one on the far right, an old favorite of mine, is from several decades ago. As you can see it's large and spacious inside. It has a stiff plastic headgear with a ratcheting size attachment so it can fit snugly to my head. It's also fitted with a forehead band for comfort. All hoods have similar wrap headgear, and it's also very important that the headgear is adjusted properly so that the hood sits in the proper position related to your face and doesn't cause undue neck strain.
In the past couple of decades we've seen enormous technological advances with auto-darkening hoods. These work with polarizing filters that are optically engaged at the instant the arc is struck. That is, you can see clearly through them before you weld, and as soon as you strike the arc the lens changes to provide the necessary UV protection. These are a lot easier to use. The disadvantage is that they can be very expensive. You can find cheaper versions but I wouldn't recommend them. A good hood like this will cost you upwards of 200 dollars. This hood is also fitted with the same kind of headgear, but you'll notice an on-off switch. In this case the optical operated auto-darkening filter operates with the aid of a battery.
You want to make sure that the helmet fits snugly and that the crown is engaged with your head. Make sure it's tight. It's also possible to adjust the stiffness of the helmet on these side dials here, and that gives you some control over whether it's easy or hard to raise and lower the hood. Basically you want that to be tight enough so that the hood will stay in the position that you want it to, either up or down.