This can be considered as enclosed premises in which purging stream of safe atmosphere is continuously maintained so that no opening therein may be a point of ingress of gases or vapor coming from an external source of hazard.
Pipes carrying petroleum or petroleum products laid in the open outside hazardous area can be classified as safe area. Area in which by which combustion occurs due to process requirement such as boilers, furnaces where by nature design requires safety features of the mechanical equipment to virtually render the risk of release of hazardous gases an vapors as non existent can also be considered as safe area.