The optimum humidity level for humans is between 45 and 55 percent, according to Bright Hub Engineering. People can tolerate humidity from 20 to 60 percent, and the comfortable range for living conditions is 30 to 50 per... More »

Indoor humidity levels should be kept at 50 percent or lower. Keeping humidity down helps to keep mold and spores at bay, and helps to cool the home. More »

Maintaining an indoor relative humidity of approximately 45 percent is the ideal level for the summer months or warmer climates. Colder climates or the winter months require even lower levels, approximately 30 to 40 perc... More »

A normal carbon dioxide level for humans is 23 to 29 milliequivalents per liter, states MedlinePlus. CO2 is primarily found in the form of bicarbonate. A blood test determines how much bicarbonate is in the serum or liqu... More »

The optimum pH levels of the human body vary depending on the specific body part, states the Journal of Environmental and Public Health. For example, the stomach has a very acidic pH range of 1.35 to 3.5, while the bile ... More » Health Medical Ranges & Levels

Generally, normal oxygen levels in humans range from 95 to 100 percent, and less than 90 percent is considered low, according to Mayo Clinic. A low blood oxygen level, called hypoxemia, can cause shortness of breath. Art... More »

Although the average blood pressure of humans varies due to many factors, WebMD cites normal human blood pressure as being a systolic pressure of less than 120 and a diastolic pressure of less than 80. Blood pressure hig... More » Health Medical Ranges & Levels