What are the long-term effects of carbon monoxide poisoning?

Likely none. Carbon monoxide acts by keeping red blood cells from picking up oxygen so it hurts you by starving the body for oxygen. Once the co separates off the red cell it starts working again and theprocess stops. It the lack of oxygen was severe enough to cause damage to parts of the body it will take time for that to be repaired, but otherwise there shouldn't be long-term problems.