bacteria (LDB) cannot survive without water, and a properly operated, well-maintained HVAC system is unlikely to be a source of problems unless water contaminated with the bacteria enters the system. Air conditioning units without humidifiers have not been identified as sources ofFor a Legionnaires' disease outbreak to be linked directly with the HVAC system, LDB-contaminated water must enter the system, be aerosolized, and be delivered to building occupants. to consider in the system design Operate and maintain all HVAC equipment as originally designed, and maintain it so that it can perform as designed. Minimize use of water reservoirs, sumps, and pans. Provide a way to drain water sumps when not in use, such as, an electric solenoid valve on the sump drain. Provide a "bleed" for water sumps so that dissolved solids do not form sediments in the sump. Slope collection pans and drain sumps from the bottom so that all the water can drain out and allow the pan to dry.

Locate HVAC fresh-air intakes so that they do not draw the mist from a cooling tower, evaporative condenser, or fluid cooler into the system. car ac repair topeka ksWhen evaluating this path, consider:air handling unit bim Prevailing wind direction and velocity.daewoo portable ac unit Building effects such as low-pressure zones on leeward sides of buildings and on roof. Distance from tower to intake. Design indirect evaporative cooling systems with the knowledge that the failure of the heat exchanger will allow wet systems to mix with the air-distribution systems. Do not use raw steam from the central heating boiler to humidify air because it contains corrosion inhibitors and anti-scaling chemicals. Atomizing humidifiers should have contaminant-free water.

to maintain a HVAC system Properly drain all sumps and permanently drain inactive sumps to prevent accumulation of sediments. If an HVAC sump is used during the hours when a building is occupied, drain the sump during unoccupied hours. Maintenance failures can produce stagnant water that can become an ideal environment for LDB growth if sufficiently warm (such as heated by sunlight). To effectively control contamination, be aware of the conditions that may promote growth and distribute External sources may emit contaminated aerosolized water that is drawn into a system's fresh-air intake. Fresh-air intake airways, typically concrete plenums located at grade level, supplying fresh air to air handlers in the basement or lower levels of buildings can collect organic material (such as leaves and dirt). Aerosols from spray irrigation. Internal sources may provide contaminated aerosolized water that is then disseminated by the air-distribution system.

HVAC system humidifiers are potential sources of aerosol exposure if contaminated II:B. Humidifiers and Misters. Direct evaporative air coolers with sprays or misters used as humidifiers include sumps, which may stagnate when not in use. Indirect evaporative air cooling systems using water coils may develop a leak that may inject cooling tower water directly into the supply air stream. Air-to-air heat exchangers may develop leaks, which may allow the wet air stream to mix with supply air and cause problems if the wet air stream is contaminated with Wet evaporative coolers, slinger air coolers, and rotary air coolers with improperly operated and maintained systems that use warm, stagnant sump water may be potential sources of Residential humidifiers, such as free-standing or portable units, often contain sumps that are frequently contaminated with Computer room air conditioners may contain a humidifier sump filled with contaminated water. Improperly drained condenser pans may produce tepid conditions that can encourage microbial and fungal growth.

Should HVAC systems be sampled? Note: There is no reliable way to detect nonviable LDB in the air. For additional information, see Section II:B. Humidifiers and Misters: Sampling Protocol, and Section II:E. Water Sampling Guidelines: Monitoring. to treat a contaminated system LDB is detected, follow these steps for treatment: Eliminate all water leaks and remove any standing water found in the system to ensure future drainage. Replace or eliminate any water-damaged insulation in the system. Operate the HVAC system using 100 percent outside air for eight hours before returning the building to normal operation. When the building is returned to normal operation, keep outside-air supply rates as high as possible for one month. At a minimum, the outdoor air requirements of ASHRAE Ventilation Standard 62-2001Causes, How it Spreads, and People at Increased Risk Causes and Common Sources of Infection How it Spreads People at Increased Risk Español: Causas y transmisión

Causes and Common Sources of Infection Legionella is a type of bacterium found naturally in freshwater environments, like lakes and streams. It can become a health concern when it grows and spreads in human-made water systems like Hot tubs that aren’t drained after each use Hot water tanks and heaters Cooling towers (air-conditioning units for large buildings) Home and car air-conditioning units do not use water to cool the air, so they are not a risk for Legionella growth. This bacterium grows best in warm water. After Legionella grows and multiplies in a building water system, that contaminated water then has to spread in droplets small enough for people to breathe in. People are exposed to Legionella when they breathe in mist (small droplets of water in the air) containing the bacteria. One example might be from breathing in droplets sprayed from a hot tub that has not been properly cleaned and disinfected. Less commonly, Legionella can be spread by aspiration of drinking water, which is when water “goes down the wrong pipe,” into the trachea (windpipe) and lungs instead of down the digestive tract.

People at increased risk of aspiration include those with swallowing difficulties. In general, Legionnaires’ disease and Pontiac fever are not spread from one person to another. However, this may be possible in rare cases. If you have reason to believe you were exposed to the bacteria, talk to your doctor or local health department. Your local health department can determine if an investigation is needed. Be sure to mention if you spent any nights away from home in the last two weeks. People at Increased Risk Most healthy people do not get sick after being exposed to Legionella. People at increased risk of getting sick are: People 50 years or older Current or former smokers People with a chronic lung disease (like chronic obstructive pulmonary disease or emphysema) People with a weak immune system from diseases like cancer, diabetes, or kidney failure People who take drugs that suppress (weaken) the immune system (like after a transplant operation or chemotherapy)