Related Clues:

• Argon and xenon, e.g.
• Some cause laughter
• Atmospheric mix
• Aerostatics subject
• Some are noble
• They're in the atmosphere
• Krypton and oxygen, e.g.
• Exhausts, say
• Neon and hydrogen
• Some elements
• They're in the air
• They can cause tears or laughter
• Argon and xenon
• Krypton and xenon, e.g.
• Some may be noble