Possible Clues:

• Firmly sealed composition that's difficult to obtain
• Sealed completely, perhaps
• Look mean, not letting out a breath?
• Mixture of gases hazardous — could be sealed
• Publicise compact, securely sealed
• Like perfect alibis
• Secure display first that is atmospherically impenetrable
• Firmly closed broadcast having had excess booze
• Solid, alibiwise
• Lay drunk maybe beyond question