The chemical that can absorb all the oxygen in the air of a room, car, or any small space is called a "oxygen absorber" or "oxygen scavenger." These substances are typically used to control oxygen levels in enclosed environments or food packaging to prevent spoilage or oxidation. Oxygen absorbers commonly contain iron powder, which reacts with oxygen through oxidation, effectively removing oxygen from the surrounding air. This process helps to extend the shelf life of products and maintain their quality.