Ethylene

Besides the Barium we got some of this:

High concentration in air

• Percent of O₂ saturation at 64 to 82%
• Compensatory mechanisms increasingly become inadequate
• Air hunger, gasping for breath
• Fatigue, lassitude, inability to maintain balance
• Tunnel vision, out-of-body experiences
• Dizziness
• Mild to persistent headache
• Belligerence, certainty of truth
• Extreme euphoria, belief in capacities of the self enhanced
• Visual acuity is reduced, dreamlike seeing of visions
• Numbness and tingling of extremities
• Hyperventilation
• Distortions of judgment, abnormal or illogical inferences drawn
• Memory loss after event
• Increased cyanosis
• Decreased ability for escape from toxic environment

more: http://en.wikipedia.org/wiki/Ethylene#Symptoms