Can air conditioning make you sick? What federal and Florida health agencies say

Legionnaires' disease and home air conditioners

The EPA says Legionella bacteria can cause Legionnaires' disease, a serious type of pneumonia, and Pontiac fever, a mild respiratory illness. The CDC says pneumonia is an infection of the lungs.

The CDC says people can get these illnesses when they breathe in small droplets of water that contain the bacteria. It says that, in general, people don't spread these illnesses to other people.

Here is the key point for homeowners. The CDC says home and car air-conditioning units don't use water to cool the air, so they aren't a risk for Legionella growth. It adds that this includes window units, such as the kind seen at some hotels.

The CDC says cooling towers are structures that contain water and a fan as part of centralized air-cooling systems for buildings or industrial processes.

Mold, moisture and allergies

The Florida Department of Health says all molds require water to grow. The Florida Department of Health's mold page says: routinely inspect the evaporator coils, liner surfaces, drain pans and drain lines.

The EPA says cooling coils are designed to remove water from the air. It says they can be a major source of moisture contamination that can lead to mold growth.

The EPA says molds produce allergens, which are substances that can cause allergic reactions, along with irritants. It lists hay fever-type symptoms, such as sneezing, runny nose, red eyes and skin rash. It also says molds can cause asthma attacks in people with asthma who are allergic to mold.

The CDC says exposure to damp and moldy places may cause a variety of health effects, or none at all. It says people with asthma or a mold allergy may have severe reactions. Immune-compromised people and people with chronic lung disease may get infections in their lungs from mold.

The Florida Department of Health says allergic disease is now considered the most likely health problem related to mold exposures. For where mold hides inside a system, see our guide to mold in HVAC systems.

Keeping indoor humidity low

The CDC says an air conditioner or dehumidifier will help you keep indoor humidity low.

The EPA says to keep indoor humidity low and to use air conditioners or dehumidifiers when needed. It also says to keep air conditioning drip pans clean and drain lines flowing properly.

The Florida Department of Health makes a Florida point directly. It says that stopping air conditioning over suspected mold would make most Florida buildings very uncomfortable during hot and humid weather.

The EPA says not to run the heating, ventilation and air conditioning (HVAC) system if you know or suspect mold in it. It says this could spread mold through the building. For humidity targets, see our guide on good humidity for a house.

Sick building syndrome

An EPA fact sheet says the term sick building syndrome is used to describe situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified.

The symptoms it lists include headache, eye, nose or throat irritation, dry cough, dry or itchy skin, dizziness, nausea, trouble concentrating and fatigue. It says most of the people who complain report relief soon after leaving the building.

The fact sheet says inadequate ventilation is thought to be an important factor. The fact sheet says inadequate ventilation may also occur if HVAC systems do not spread air well to the people in the building.

This fact sheet is from 1991 and speaks of building occupants generally. It also says complaints may have other causes, and that the specific cause may remain unknown even after an investigation. Our ventilation guide covers how outdoor air reaches a home.

Colds, sniffles and how to tell what is going on

The CDC says colds are caused by different respiratory viruses, and that rhinoviruses are the most frequent cause in the United States. It says most respiratory viruses are spread through droplets that an infected person releases when they cough or sneeze.

The CDC also says you can get a cold any time of year.

The EPA does say some indoor air effects are similar to those from colds or other viral diseases, so it advises paying attention to the time and place symptoms occur.

The EPA adds that some effects may be made worse by too little outdoor air or by the heating, cooling or humidity conditions indoors.

The CDC says to use air conditioning

The CDC's heat and health page tells people to use air conditioning or find a place that has it. It says you can find one by dialing 2-1-1 or by contacting your local health department or emergency management agency.

The CDC also warns about fans. It says to use fans only if indoor temperatures are less than 90 degrees Fahrenheit. Above that, it says a fan can increase body temperature.

The CDC names groups that may need to take extra steps on hot days. They include people with asthma, especially children, people with heart disease, pregnant women, people 65 or older, infants and young children, and people working or exercising outside.