Exhaled breath is primarily composed of nitrogen (N₂), oxygen (O₂), carbon dioxide (CO₂), and water vapor (H₂O). These are the major components, making up the vast majority of the air we breathe out. However, there are also trace amounts of other elements and compounds present, including:

Gases:

* Argon (Ar): An inert gas present in small amounts in air.

* Helium (He): Another inert gas, though its concentration in exhaled breath can be higher if the person has recently inhaled helium.

* Neon (Ne): An inert gas, present in trace amounts.

* Krypton (Kr): An inert gas, present in trace amounts.

* Xenon (Xe): An inert gas, present in trace amounts.

* Methane (CH₄): Produced by bacteria in the gut and can be exhaled.

* Hydrogen (H₂): Produced by bacteria in the gut and can be exhaled.

* Carbon monoxide (CO): Can be present in exhaled breath if the person has been exposed to smoke or other sources of CO.

* Nitrous oxide (N₂O): Can be present in exhaled breath if the person has been exposed to anesthetic gases or certain medications.

Volatile Organic Compounds (VOCs):

* Acetone (CH₃COCH₃): A byproduct of metabolism that is present in small amounts in exhaled breath.

* Isoprene (C₅H₈): Produced by the body and can be exhaled.

* Ethanol (C₂H₅OH): Can be present in exhaled breath if the person has consumed alcohol.

* Other VOCs: Many other VOCs can be present in exhaled breath, depending on factors like diet, health status, and exposure to environmental pollutants.

Other elements:

* Sodium (Na): Present in trace amounts.

* Potassium (K): Present in trace amounts.

* Calcium (Ca): Present in trace amounts.

* Other elements: Trace amounts of other elements may be present, depending on the individual's health status and diet.

The exact composition of exhaled breath can vary depending on factors such as age, sex, diet, physical activity, and health status.

It's important to note that analyzing the composition of exhaled breath can be used for diagnostic purposes. For example, the presence of certain VOCs in exhaled breath can be indicative of certain diseases or conditions.