The most important chemical regulator of respiration in a healthy individual is carbon dioxide. Respiration involves exchanging oxygen and carbon dioxide between the air and a person's blood. When brain receptors perceive too much carbon dioxide in the blood, they signal the body to increase ventilation.
The blood pH levels are inversely related to the amount of bloodborne carbon dioxide. An increase in carbon dioxide results in a decrease in the pH levels of the blood, causing the person to increase his rate of ventilation.
Another important chemical regulator of respiration is oxygen. When oxygen levels in the body drop, carotid and aortic chemoreceptors respond by increasing ventilation.