Level A - the most hazardous, requires fully incapsulated chemical resistant protective clothing that provides full body protection as well as SCBA and special sealed equipment
Level B requires non encapsulated protective clothing, or clothing that is designed to protect a particular hazard. (usually this clothing is made of material that will let only limited amounts of moisture and vapor.
Level C - like level B, requires the use of nonpermeable clothing and eye protection. In addition, face mask that filter all inhaled outside air must be used.
Level D - requires a work uniform, such as coveralls, that affords minimal protection
This protection levels are utilized depending on the classification of Hazardous Materials according to health hazard or toxicity levels, fire hazard and reactive hazard.
Toxicity Levels of Hazardous Materials
Level Health Hazard Protection Needed
0 Little or no Hazard - None
1 Slightly Hazardous Self Contained Breathing Apparatus (level C suit)
2 Slightly Hazardous Self Contained Breathing Apparatus ( level C suit)
3 Extremely Hazardous Full protection, with no exposed skin (level A or B)
4 Minimal Exposure causes Special Hazmat gear (level A suit)