Air Solution Company - Helping to Maintain Healthy Evaporative Cooling Systems

Legionnaire's Disease (Legionellosis) and EvaporativeEvaporative Cooling Systems.
Cooling System Maintenance RecommendationsBased upon a six-year committee effort, ASHRAE
What is Legionnaire's Diseaseboard of directors approved guidelines (known as
It is a bacterial infection that is characterized byguideline 12) that provides environmental and
pneumonia. According to the Center for Diseaseoperational guidelines for maintaining safe evaporative
Control (CDC), legionnaire's disease is caused bywater cooling systems. The guidelines are intended
bacteria known as Legionella pneumophila. There arefor use by: commercial cooling system designers,
at least 43 species of legionella however, it is themaintenance engineers, equipment manufactures,
Legionella pneumophila strain that causes over 90%owners, operators and users.
of legionnaire disease deaths.Key Maintenance Recommendations (Guideline 12)
In the United States, it is estimated that as many as- Keep system clean using a microbial treatment
18,000 cases occur each year. Death results in 5 -program.
15% of the cases.- Use a qualified water treatment consultant to
Legionella are commonly found in low concentrationsestablish and oversee a water treatment program.
in both natural and unnatural (man-made) aquatic- Keep system free of debris that can contribute to
environments. Within unnatural environments, wherethe food source for legionella. (Air Intake Filters can
water is used in an evaporative heat exchangehelp to control debris and organic material build-up).
process, warm temperatures combined with poorly- Inspect and clean cooling equipment if it is found to
treated cooling water can create an environmenthave a build-up of dirt, organic matter or other debris.
ideal for proliferation of this deadly bacteria.- Inspect drift eliminators and clean or replace as
Because cooling towers, evaporative condensers andneeded.
chillers are highly efficient at drawing large volumes of- Keep maintenance and operational records that
air to support the evaporative cooling process,include equipment manufacturers maintenance
airborne organic material such as leaves, insects,manuals, description and dates of the water
pollen, birds, cotton wood and other debris is usuallytreatment program, inspection dates, MSDS
drawn into the water system and if not maintaineddocumentation on all treatment chemicals, equipment
can accumulate, decompose and contribute torepair records including dates, system water volume
system fouling and microbial growth including legionellarecords, and the names and phone numbers of
pneumophila.individuals responsible for system start-up,
Ideal conditions for legionella proliferation includemaintenance and shut-down.
water temperatures between 77 - 108 degreesCooling Tower Locations Recommendations (Guideline
Fahrenheit (25 - 42 degrees Centigrade), presence of12)
organic debris, sediment, scale, stagnant conditions- Locate cooling towers far from fresh air intakes
and presence of amoebae. Legionella naturally preysand windows that can be opened.
on amoebae and incidentally prey on phagocytic cells- Consider prevailing wind direction and don't locate
(part of human immune system) when inhaled thusupwind or upstream of outdoor public areas.
leading to Legionnaire's Disease. The legionella bacteria- Don't locate in areas that can contribute debris and
is transmitted by aerosol (mist) from devices such asorganic material.
cooling towers showers and faucets and aspiration of- Consider the direction of prevailing winds and don't
contaminated water. Person-to-Person transmissionlocate upstreamof any outdoor public areas.
does not occur.- Consider future construction, including that on
Controlling Legionella in Cooling Towers &nearby sites.