The type of equipment that a volcanologist would wear in the field depends on what they are doing.

Most of the time when they work on a volcano, they just wear a pair of heavy boots, jeans, hat, and long-sleeved shirt to protect from sharp dried lava.

They might use heavy work gloves if they are working on fresh lava flows and a rock-climbing helmet if working in an area where there is a lot of rock fall.

If needed they might wear a fire-retardant flight suit, a gas mask, or a flight helmet.   

They might use one of the silver heat-resistant suits but it honestly does happen very rarely, most of the time these suits are too bulky and difficult to move around in to make them practical field gear.

Studying Volcanoes / Volcanology