Any ACR contractor who hasn’t been asked some unusual or surprising questions by customers is likely very new to the job. One question that’s becoming less and less unusual, however, is something along the theme of “Will this air conditioner put me at risk of catching Legionnaires’ disease?”

Anyone who has a degree of familiarity with ACR technology should know that the answer is of course no. However, if you’re going to be able to reassure customers that this is the case, you’re probably going to need to display more detailed knowledge than this. I’ve compiled a quick guide to Legionnaires’ disease and home building systems which should allow you to allay your customers’ fears.

The bottom line

The bottom line, and the most pressing thing that you need to get across to customers, is simply that air conditioners do not cause Legionnaires’ disease, nor are they the most significant factor in allowing it to spread.

Legionnaires’ disease, you should be able to explain, is most commonly caused by the inhalation of the Legionella bacteria after it has been dispersed into the air via water droplets. The bacteria survives and multiplies in dirty water that has been kept within a certain temperature range (more on this later). Since air conditioners don’t carry any water inside their systems, they cannot be the origin of the bacteria inside a building. The air conditioner’s only culpability in the process is that it can allow contaminated air to spread around a large building. Even though by this point the damage has already been done, this is likely how the myth of the air conditioner as the “cause” of Legionnaires’ disease has persisted.

The real risk

Once you’ve explained this, your customer is quite likely to ask where the disease does come from. You can explain to them that likely hiding places for the bacteria include cooling towers, whirlpool spas, showers that draw water from a hot water storage tank, and humidifiers -- a recent outbreak at a South Tyneside factory was traced to the cooling towers.

When water is kept in rusty conditions, or is routinely recirculated, or is stored at temperatures ranging between 25 and 45 degrees centigrade, then you’ve got an optimum breeding ground for Legionella bacteria. A good point to remember and impart is that customers are at much, much higher risk of contracting the disease from an old system that’s been poorly maintained than from something new like a freshly installed air conditioner.

An additional point is that the risk is minimal. Legionnaires’ disease is thankfully rare, which is one of the reasons an outbreak can reliably make headlines when it does happen. Still, it’s worth advising customers that if they experiences symptoms comprising some combination of fever, chills, confusion, coughing, muscle aches, headaches and tiredness then they should be booking in to see a GP as soon as possible.

The preventative measures

If a customer asks what they can do to minimise their risk of the disease then direct them towards the water systems, where the bacteria is most likely to be found. A buildup of organic matter such as mould can be a factor, so regular cleaning is a must. They also need to look at the water temperature -- as mentioned, if domestic water is routinely being stored between 20 and 45 degrees centigrade then Legionella bacteria will be able to multiply. Regularly heating the water to a temperature higher than 60 degrees is an excellent countermeasure to this. If your customer is an employer or a landlord then they have a legal responsibility to carry out risk assessments for Legionella -- there’s a good FAQ here that’s worth directing customers to.

Final thoughts

Despite the fact that the connection between air conditioners and Legionella is grossly over-exaggerated, the fact that the myth has become widespread and tenacious means that you need to be familiar with the basics in order to set your customers’ minds at ease. The more knowledgeable you are, the more reassured your customer will be, so keep all these points and facts in mind and you needn’t ever be stumped by a worried customer.