
A Hazardous Location (HazLoc) is where fire or explosion hazards may occur due to flammable:
Gases/vapors
Liquids
Dust
Fibers
HazLocs are broken up into three different classes depending on what flammable materials are floating around in the air. These hazardous locations are in nearly every industry; from textiles and the fashion industry, to agriculture and farming, to power generation, breweries and distilleries, government and military, and more.
Class I Locations
These locations have flammable gases/vapors in the air in quantities large enough to be explosive or ignitable. The potential for explosion happens when an electrical object or channel or other source of ignition is present. According to OSHA, some examples are:
Petroleum refineries, and gasoline storage and dispensing areas
Dry cleaning plants where vapors from cleaning fluids can be present
Spray finishing areas
Aircraft hangars and fuel servicing areas
Utility gas plants, and operations involving storage and handling of liquified petroleum gas or natural gas

Class II Locations
This type of location is classified by the presence of combustible dust in the air in large enough quantities to be explosive. Some examples of this location according to OSHA are:
Grain elevators
Flour and feed mills
Plants that manufacture, use or store magnesium or aluminum powders
Producers of plastics, medicines, and fireworks
Producers of starch or candies

Class III Locations
The last type of location is classified by the presence of easily-ignitable fibers or “flyings.” These types of flammable materials (like threads) aren’t hanging in the air, but rather collect around equipment or on lighting fixtures where heat, sparks, or heated metals may ignite them. Examples of these kinds of HazLocs (according to OSHA) are as follows:
Textile mills, cotton gins
Cotton seed mills, flax processing plants
Plants that shape, pulverize or cut wood and create sawdust or flyings

These easily-ignitable materials affect nearly every industry. That is why it is so important to have the right kind of explosion-proof housings for security cameras and systems, to help prevent disaster at a given facility. Our unit minimizes any possibilities of electrical wiring and equipment becoming a source of ignition in volatile places, and is ideal for petroleum refineries, chemical plants, oil tankers, offshore platforms, industrial processes, food manufacturing facilities, gas pipelines, grain storage centers, and more. Read more here.
Source
https://www.osha.gov/sites/default/files/2018-12/fy07_sh-16615-07_haz_locations_handout.pdf