People contract Legionella pestis from water droplets. International research shows that there is no realistic chance of contacting Legionella pestis from a sprinkler system when it operates. Current thinking is that the water droplet sizes generated by sprinkler head deflectors are too large to pass through the membranes of the lung and this, together with the fact that the oxygenation, pH and temperature of the water in sprinkler pipes does not provide a suitable environment for the Legionella bacteria to flourish suggests that there is no substantive issue.

Additionally, there are no recorded cases of anyone contracting Legionella from a sprinkler system anywhere in the world.