Deferent between hot work permit and cold work permit?

Any of the activity which release spark is considered as Hot Work Activity like Welding Cutting Grinding

Whereas any of the activity which doesn't release any of the spark is considered as Cold work such as Scaffolding erection, Excavation, Lifting etc  

A hot work permit is required for any work that develops spark,flames, or heat sufficient to cause ignition. A cold work permit is used for work that will not produce sufficient energy to ignite flammable atmospheres or materials

A hot work permit refers to any situation which arises flames, sparks etc to cause ignition. fire. 

A cold work permit refers to  situations which will NOT lead to ignition at workplace or materials. It will not create a flamable atmosphere.