What are the two types of valves that need to be closed when a flashback occurs?

When a flashback occurs, it is essential to immediately close both oxygen and acetylene valves to prevent further combustion and potential explosion. Flashbacks can occur when there is a reverse flow of gases into the hoses, which can ignite and travel back into the supply line. By shutting off the oxygen and acetylene valves, you cut off the fuel supply, stopping the combustion process and allowing for more controlled handling of the situation.

The oxygen and acetylene gases are the primary fuels used in oxy-acetylene torch operations, and both need to be shut off because the mixture of these gases is what supports the flame. Therefore, controlling both allows for a safer environment and reduces the risk of fire hazards following the incident.