Possible Clues:

• It should contain a fire
• Like the finest old style fireproof material
• A request for help to install top-quality insulating material
• Criminal set restrained by orders we now know to be dangerous
• The way even the best noughts are no good for the fire
• Old construction danger
• Charlie swallowing cream egg and mineral
• What does not burn is best put in an urgent message
• Construction material no-no
• Like most good 25 down it can't be fired