We have been told that there are dangers in subjecting concrete to carbon monoxide fumes. What are they?
Carbon monoxide makes up only a small portion of the fumes from oil- or gas-burning heaters or gasoline engines and probably has no important effect on concrete. These same engines and heaters, however, pour out vast amounts of carbon dioxide, which does affect concrete. Carbon dioxide interferes with the hydration of concrete during its early curing period and produces weak and dusting surfaces. Fumes from heaters used to keep fresh concrete warm should therefore be vented to the exterior of a building. After concrete has been fully hydrated the bad effects of carbon dioxide disappear.