How much air in the bloodstream is lethal?

The presence of air in the bloodstream, known as air embolism, can be lethal even in small amounts. Typically, an air bubble larger than 0.5 to 1 milliliter can cause significant harm, particularly if it enters the heart or brain, leading to serious complications like stroke or cardiac arrest. The exact lethal volume can vary based on individual physiology and the location of the embolism, but prompt medical intervention is crucial to mitigate the risks.