Produce Misting Sytems: An Unusual Risk for Legionnaires’ Disease?
In this article our legionella risk specialists review the use of produce misting systems in supermarkets and food stores, and ask whether this type of humidification system creates an increased risk of Legionnaires’ disease.
The article explains what this type of misting system is and how it works. It goes on to consider where legionella risks can crop up and how such systems should be installed and maintained to keep them safe`. It concludes by reviewing the management processes required to maintain safety including the allocation of responsibilities, and the importance of a risk assessment and development of a scheme of control.
A version of this story dealing with produce misting systems and the potential for Legionnaires’ disease first appeared in Legionella Control International’s newsletter. To get it in your inbox, sign up for free here.
What are produce misting systems?
Most people aren’t aware of retail humidification and produce misting systems, much less seen them in action. Yet most fresh produce (fruit and vegetables, fish, meat etc.) will quickly lose its freshness if a misting system is not in place. This type of humidification system or fogger can release moisture into the air, making fresh fruit and vegetables look more attractive, last longer, and retain moisture to help with both those elements.
Yet as with all other machines and water sources that create an aerosol releasing water droplets in to the atmosphere, there is an inherent risk of Legionella bacteria being released as well. If this was to occur, there is a real chance of customers and workers within a supermarket or food store being exposed to Legionella bacteria, the organism that causes Legionnaires’ disease.
An outbreak of Legionnaires’ disease would clearly be a serious incident for any food store of any size. Fortunately, there is no reason why retail misting systems should not be well maintained and cared for, so they can safely be used throughout the fresh produce areas of the supermarket when needed.
Making sure supermarket misting systems are properly installed
In some cases, retail misting systems are built into the displays that hold the fruit and vegetables, fish, meat etc. and are therefore out of sight. This should never mean they are out of mind, however. Indeed, a permanent misting system like this should be properly installed so that every part is necessary for its use. There should be no runs of piping or dead legs anywhere, as these raise the risk of stagnant water. This in turn means biofilm and sediment is more likely to congregate in that area, offering any Legionella bacteria that has contaminated the water system a viable food source to help it multiply. This could lead to the bacteria more easily spreading throughout the misting system to increase the risks associated with Legionnaires’.
Maintaining produce misting equipment once in use
Even when a produce misting system is properly installed with an eye to regular use and no dead legs to raise the risk of bacteria multiplying in those areas, inadequate maintenance is still a potential red-flag. For example, the water temperature should always be at a suitable level. Legionella bacteria love being in water that is between 20 – 45 degrees Celsius, so the water temperature used in the misting system should be below 20 degrees Celsius, assuming it is kept cold. If, for any reason, water needs to be heated, it should always be above 50 degrees Celsius to kill off any Legionella bacteria that is present.
It is also vital to pay attention to disinfectant levels within the produce fogger system. Disinfectants help get rid of legionella and many other bacteria that could potentially cause harm if they were to reach the fresh produce via the misting system. Therefore, regular maintenance should always consider this, and make sure that, where appropriate, the correct level of food-safe disinfectant is always used.
Are you certain you’re maintaining your misting system correctly?
The information given thus far in this article makes sense. If you’re installing anything, you need to be sure the equipment is designed correctly and that it is fitted properly. You also need to make sure you are following all proper maintenance procedures to keep the system clean and risk free. Without these, as we’ve seen, any produce misting system is going to be at risk from legionella and other waterborne bacteria. Even a brand-new humidification system has the potential to be colonised by bacteria if it is not maintained to the required standards.
Who’s responsible and the legionella risk assessment process
Firstly, someone with relevant knowledge and experience should be responsible for managing the safety of the system, cleaning and any maintenance processes required. Knowledge of Legionella bacteria, how it can spread through a water system, and how it is controlled is vital.
A legionella risk assessment is your first step, as this will identify where any risks lie, and what can be done to control them. This should be followed by a scheme of control that will set out practical measures that need to be taken to control the risks.
All misting systems will be comprised of several working parts, and these should be regularly taken apart and thoroughly cleaned, making sure the proper cleaning tools and liquids are used for each part. The manufacturer should supply full instructions on when and how to clean the system, but careful attention should also be paid to Health and Safety rules as well. In all cases, the Health and Safety Executive codes of practice and guidance dealing with the control of legionella (ACOP L8 and HSG274) should be most important and always adhered to.
In some cases, where suitably trained staff are not available to keep the misting system safe for use, it may be prudent to call in experts, such as Legionella Control International, who are trained to know how to maintain the system for safety. In other cases, training courses might work, where the person or persons responsible for maintaining and cleaning the system take part in courses to give them the knowledge needed to do their job correctly.
Is there a real risk of contracting Legionnaires’ disease from produce misting systems?
Yes, but the risk is thought to be very small with well-designed and correctly maintained systems. However, this does not mean those responsible for supermarkets and food stores that use misting systems can forget about maintenance and cleaning. In most cases, the reason there are no outbreaks that can be traced to such equipment is because those responsible for them are taking their responsibilities seriously. This alone is reassuring, but if you need to install, maintain, and clean retail humidification misting systems as part of your job role, you must make sure you do so correctly. This will help ensure the risks associated with Legionella bacteria and Legionnaires’ disease remain under control to keep shoppers, colleagues and others safe.
Legionella and water safety specialists
Our teams of legionella and water safety specialists support those responsible for water safety and the control of legionella in all types of water system, helping them to protect people and meet their health and safety obligations in this specialist area.
We deliver professional water safety risk assessments for legionella and other waterborne pathogens, water testing, independent compliance auditing, City & Guilds training and other environmental risk management services that help keep employees, guests and others safe.
To speak with one of our legionella specialists’ call us today on 0330 223 36 86 or contact us here …
