The air in Colorado is thinner than at sea level due to the state’s geography, which is dominated by the Rocky Mountains. Many major population centers and vacation destinations are situated at elevations significantly higher than the coast. This increased elevation directly results in less dense, or “thin,” air.
The Physics of High-Altitude Air
The primary reason air thins with elevation relates to atmospheric pressure, which is the force exerted by the weight of the air column above. At sea level, a massive column of air presses down, resulting in high pressure and dense air. As you ascend to the elevations common in Colorado, the column of air above you shortens, causing the atmospheric pressure to drop significantly.
For example, Denver, known as the “Mile High City,” sits at approximately 5,280 feet, and the atmospheric pressure there is about 15 to 18 percent lower than at sea level. This drop in pressure means that while the air still contains about 21 percent oxygen, each breath contains fewer total gas molecules, including oxygen.
Many mountain towns and ski resorts are situated far higher than Denver, intensifying this effect. Leadville, for instance, is the highest incorporated city in North America at 10,152 feet, and the town of Alma is higher still at 10,578 feet. At these elevations, the atmospheric pressure is reduced even further, meaning the body receives substantially less oxygen with every breath.
How Thin Air Affects the Human Body
The body’s immediate response to the reduced oxygen availability is to increase ventilation. Your body compensates for the lower oxygen per breath by increasing your breathing rate and depth, which is why you may find yourself breathing faster or feeling short of breath, especially when exerting yourself. This increased respiratory effort is a short-term adjustment to enhance the oxygen supply to the tissues.
For visitors, the most common concern is Acute Mountain Sickness (AMS), which typically occurs at elevations above 8,000 feet, though some people feel effects lower down. Symptoms of AMS can include headache, nausea, dizziness, and general malaise, and they usually begin within 6 to 12 hours of arrival. These effects result from the body struggling to maintain its necessary oxygen levels and the subsequent fluid shifts and changes in blood chemistry.
Over a period of days to weeks, the body undergoes a more profound process called acclimatization. The kidneys respond to the low oxygen by releasing a hormone called erythropoietin, which stimulates the bone marrow to produce more red blood cells. This increase in red blood cells, a process known as polycythemia, enhances the blood’s capacity to carry oxygen, offering a long-term adjustment to the thin air.
Navigating Life and Travel at Elevation
Increased hydration is particularly important because the low humidity and increased breathing rate cause the body to lose water through respiration at twice the rate it does at sea level. It is recommended to significantly increase fluid intake, often by an extra liter or more per day, to counter this effect and aid in the acclimatization process.
Visitors should also be mindful of their alcohol consumption, as its effects are often amplified at altitude. Although studies suggest that altitude does not change the rate at which the body metabolizes alcohol, the combination of alcohol and low oxygen exacerbates impairment, making people feel intoxicated more quickly. Alcohol also acts as a diuretic, further accelerating dehydration and interfering with the body’s ability to sustain the increased breathing rate necessary for acclimatization.
The lowered atmospheric pressure also affects cooking, particularly methods involving boiling. Water boils at a lower temperature at altitude—for instance, at 5,000 feet, water boils at about 203.2 degrees Fahrenheit compared to 212 degrees at sea level. This requires longer cooking times for boiled or simmered foods to ensure they are fully cooked, sometimes requiring up to 25 percent more time for moist heat methods. For baking, the rapid expansion of leavening gases means adjustments are needed, such as reducing baking powder and increasing liquid and flour to strengthen the structure of the baked good.