Which class of flammable liquids can be stored beneath ground level if sprinklers are present?

Class IIIB flammable liquids can be stored beneath ground level if sprinklers are present due to their characteristics and lower hazards associated with them. Class IIIB liquids have a flash point of 140 °F (60 °C) or higher, which means they are less volatile and have a lower potential to ignite compared to more flammable classes.

The presence of sprinklers enhances safety by providing automatic fire suppression, which is essential when storing liquids that, while still flammable, carry a reduced risk. This allows for more flexible storage options in laboratory settings, as the hazards can be effectively managed with appropriate fire protection measures.

In contrast, other classes of flammable liquids have stricter regulations regarding underground storage due to higher flammability risks. Classes I and II present greater ignition risks and are subject to more stringent storage requirements to prevent fire hazards. Class IV, while less flammable, still generally does not enjoy the same allowances as Class IIIB in terms of underground storage without additional fire protection measures.