How much helium is fatal?

Inhaling helium in small amounts for a moment, such as when using it for party balloons or voice effects, is generally not fatal. However, helium is an asphyxiant; it can displace oxygen in the lungs, leading to asphyxiation if inhaled in large amounts or in confined spaces where the oxygen concentration is low. Specific quantities that might be considered "fatal" can vary widely depending on individual health conditions, the environment, and other factors. A dangerous situation can arise when helium is inhaled in such a way that it significantly reduces or eliminates the amount of oxygen available for breathing. This is particularly hazardous when done in a closed or poorly ventilated area. It's important to note that inhaling any gas not meant for respiration, including helium, can be dangerous and is not advised. If there are concerns about helium inhalation or exposure, it's best to seek immediate medical attention.