Welding produces fume made up of fine particulates and gases, and the composition varies depending on the process, the filler material and any coatings on the base metal. Fume rises from the arc and, without adequate control, can build up in the breathing zone of anyone working nearby, which is why extraction is treated as a core part of workshop set-up rather than an optional extra.
Most people buying their first welder get stuck at the same fork in the road: MIG, TIG or MMA. Each process strikes an arc differently and suits a different type of work, so the right choice depends more on what you'll be building than on which machine looks the most impressive on a shelf.
Switching speed, the time the filter takes to darken once it detects an arc, is worth checking against how you actually work rather than assuming faster is always better for every budget. For most general fabrication and repair work, a mid-range auto-darkening helmet with a sensible shade range covers the vast majority of jobs comfortably.
TIG welding relies on a handful of small consumable parts inside the torch that have an outsized effect on how the arc behaves. The tungsten electrode itself doesn't melt into the weld; it simply carries the arc, and different tungsten types, distinguished by their alloying elements, suit different current types and materials. Getting the wrong tungsten for the job typically shows up as arc wander or poor arc starts long before it shows up anywhere else.
If you're not sure which supply a particular machine needs or whether your workshop can support it, it's a sensible question to put to a supplier before ordering, and the team at
welding supplies helmets and PPE can talk through the options against your existing set-up.
Cutting capacity is usually described in terms of clean cut and maximum cut thickness, and the two are worth distinguishing. Clean cut is the thickness a machine handles with a good edge finish and reasonable speed, while maximum cut is the thickest material the machine will get through at all, usually slower and with a rougher edge. Buying with your typical material thickness in mind, rather than the thickest job you might occasionally face, generally gives a better day-to-day result.