There are several kinds of Hazmat (Hazardous Materials) gear (or "bunny suits", as they are sometimes called), giving varying levels of protection, depending upon what material is being dealt with. There are two levels of protection, Level A and Level B. Level A suits are total containment suits, giving protection from all forms of chemicals: solids, liquids, and gasses/vapors. Level B suits are not airtight, so provide protection against solids and liquids (splashing), but not vapors or gasses. This gear allows specially trained firefighters to deal with substances which may be toxic, very caustic, etc., which their normal turnout gear and SCBA may not be sufficient to protect them from. Hazmat clothing does not normally provide protection against fire or explosion; in these cases "flash" protection must also be worn.
When wearing Level A protection, it is not uncommon for the environment inside the suit to be 20-30°F (11-17°C) hotter than ambient, and 100% humidity, within minutes of sealing up the suit. Because of this, medical monitoring is required before and after working in these suits.
Hazmat gear will usually be worn in several layers, making it even less comfortable to wear. Hazmat gear consists of an air- and water-proof oversuit, booties, gloves, and a hood. These pieces are often taped up, at the ankle and wrist, so that there are no gaps for nasty things to enter. After using this equipment in a hazardous environment, firefighters will have to be decontaminated (washed off) before they can remove the protective clothing.
The first layer is often station wear (uniform) or a one-piece Nomex jumpsuit. The jumpsuit seals snuggly at the ankles, wrists, and neck, giving fire protection - otherwise, in the event of a flash fire, the plastic suit otherwise stick to the skin. The back of the jumpsuit has a large patch identifying the wearer.
The next layer of defense is a Tyvek suit. This disposable suit provides a layer that is impermeable to most chemicals. In addition, the firefighter wears an SCBA, and carries a voice-actuated radio, because once sealed inside the outer suit, there is no way to reach any of this equipment. Tyvek booties cover boots, and an inner pair of Silver-Shield chemical protective gloves is put on over latex surgical gloves. At this point, "Level B" protection is in place. An optional cooling vest, which holds ice packs, can be worn to keep the wearer cool. Some firefighters also carry a knife, in the event that they have to get out of the suit quickly in an emergency. The suit is too heavy to tear through, and would have to be cut from the inside.
The outer layer is a completely sealed, "Level A" full encapsulation suit. The suit has a one way (exhaust) pressure bleed valve. This is required because as the wearer exhales, the used air must go somewhere. Even with this valve, the suits tend to blow up like balloons. When sealed up, the wearer is completely isolated from the outside atmosphere. Nothing (hopefully) can get in, and, unfortunately, almost nothing (including body heat and sweat) can get out. These suits are comprised of up to a dozen protective layers.
Normally, another pair of protective gloves would be worn on top of these, providing four layers of protection for the hands. The gloves shown here are permanently attached to the sleeves of the suit, so that, in combination with the integral booties, no taping is required to seal the wrists and ankles, which is often necessary with other suits.
Rank hath it's privileges; these photos were taken on a 90°F (32°C) day, which is why Captain (ret.) Monique Vandenberg, modeling the cooling vest and Tyvek above, isn't the same person in the full encapsulation suit!
And, if all that isn't enough, there is one more layer which can be worn if necessary, on top of everything else. This is a flash suit, worn to protect the wearer from fire and explosions. This outer layer would be worn in the unlikely event that a firefighter had to enter an explosive atmosphere, for example to rescue a victim inside. This is a situation which would normally be avoided at all cost, except when human life is in danger. Flash suits are no longer used by this department, because the current Level A hazmat suits have flash protection built in.
Note that in this photo, the flash suit is being held up from behind, and not being worn.
If everything is being worn, the wearer has five layers of hand protection, five layers of foot protection, and is looking through three layers of protective windows. Needless to say, this isn't comfortable, and one doesn't move quickly.
These suits can cost anywhere from $4,000 - $10,000 each, and may need to be disposed of after one use, depending upon what they were exposed to and how contaminated they are.
A more complete inventory of the protective clothing carried by Hazmat 2 is available.