Acute exposure is when a person is exposed to carbon monoxide in a catastrophic type event. This is to say a boiler breaking down releasing high levels of carbon monoxide very quickly. It could also mean where a person has entered an area where there are also high levels of carbon monoxide and that person is exposed to high levels over a very short period of time.
These events are sometimes the worst kind of events in that they can lead to death. However if these incidents are picked up quickly enough and medical treatment is given then they can be very easily survivable without the long term consequences of a chronic type event. The treatment for these events is immediate oxygen and in the worst case scenario, hyperbaric treatment.
We have probably all seen a hyperbaric chamber but we would not necessarily have associated it with the treatment of these types of exposure. We may have seen a hyperbaric chamber used on TV when somebody is explaining what to do in the event of a diving incident where somebody may have had the bends. The chamber is pressurised and is fed with oxygen this enables the body to purge it self of carbon monoxide and take up oxygen on the higher pressure and therefore carry more oxygen around the body than would normally be the case. If done quickly enough then the long-term effects on the damaging the carbon monoxide to do my poisoning the body at a cellular level can be avoided.
Many people will not experience any long-term effects after an acute exposure provided the medical attention is received quickly enough. On the flip side of this if it is a catastrophic event with very high levels of carbon monoxide I'll present and the person collapses without other persons present then that person may not receive medical attention before death occurs.