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Legionella Control in Summer

Legionella control in summer

Now that the summer is finally in full swing (after a number of practice runs), thoughts quickly turn to various ways of cooling down as temperatures rise. And although it’s instinctive to look for ways to maintain our cool as the thermometer maxes out, there are hidden dangers lurking in one of the most commonly reached for currencies of cool; namely water. Chief protagonist at this time of year is of course, legionella. Not needing any introduction, legionella can crop up in a number of guises during the summer, and if you’re a business owner the potential threats might not always be that obvious. For example, such unseen menaces as air conditioning systems and humidifiers; which while in domestic settings don’t typically facilitate water as a means of cooling the air, the opposite is often true in more commercial and employee-frequented environments.

If you think about it, most air-con units are traditionally only used during the summer months; which subsequently means that throughout the rest of the year any water stored within the system becomes stagnant and a prime breeding ground for waterborne bacteria such as legionella. Cue the activation of the system at the beginning of the following summer, and bingo – the bacteria is released. Other possibly sources of legionella to be aware of at this time of year again expand on the broad subject of stagnant water heating up above and beyond legionella-avoiding maxims, and include discarded water hoses (more of which, later) and badly maintained water sprinkler systems, along with the spray emitted from a cooling tower, evaporative condensers, spa baths, showers, fountains and humidifiers.

As has already been well documented in previous blogs hereabouts, temperatures of between 20 – 45 degrees centigrade tend to be the optimum figures for legionella bacteria to breed. Therefore businesses which house installations where stored water is a prominent feature (for a range of reasons) should set ambient temperatures at either sub-20 degrees or above 60 degrees to ensure that the water source isn’t compromised by the advent of legionella-harbouring bacteria. In addition to this, any stored water should, ideally, only remain static for a period of no more than 24 hours. Although the latter is not always workable in certain commercial/industrial situations, understandably.

(Recommended reading: Legionella compliance checklist)

Monitoring of Water Storage Temperatures Key to Reducing Legionella Risk in Summer

It probably won’t come as much of a shock to learn that hitherto cold water temperatures could be prone to rise once a building warms up; especially during the summer months, all of which could have an adverse (and moreover, knock-on) effect when considering that water-containing tanks and pipes feed humidifiers, showers, sprinkler systems and an array of other assemblage found in many workplaces. Conversely pipes may have been insufficiently lagged on cold water tanks, and this insulation issue could lead to an increase in the transfer of heat absorbed by the immediate environs; again, more so on hot days. Simply put, by allowing water temperatures to exceed the recommended parameters, static water could, effectively enter the bacterial proliferation zone without business owners being any the wiser.

Realistically there are a multitude of ways in which legionella can take hold and more worryingly, be contracted by those individuals who are unknowingly exposed to aerosol droplets which are inhaled and eventually settle on human lungs (we’ll cover a few employment sectors where the risk is greater, later), and ordinarily there’s a spike in the official reporting of (the subsequently occurring) Legionnaires’ Disease here in the UK during the summer month. Public Health England readily acknowledges that the period between July and September, on average account for the peak months. As recently as 2013 some 21.8% (the equivalent of more than one fifth of all cases) of early onset symptoms of legionella occurred during August, while just 12 months earlier a headline-making outbreak of Legionnaires’ Disease brought the latent risk to the fore once again. On that particular occasion the Stoke-on-Trent outbreak – which claimed the lives of 3 people, while a further 21 were diagnosed and treated - was traced back to the bacteria presenting in an unclean display hot tub at a bargain warehouse. Which obviously means the general public are no less at risk than employees operating in more legionella-prone workplaces.

Perpetuating this sorry statistic, and here and now at the start of summer 2017, Legionnaire’s Disease has both made the front pages once more, and tragically claimed another victim. Several media outlets recently published the story of a gardener from Norfolk who succumbed to the potentially fatal health condition a few months back; in the aftermath of unwittingly inhaling toxic bacteria that was left to prosper on a garden hose (and which was subsequently activated at the juncture when the deceased was hosing down their outside terraced area and thus releasing the deadly spores into his immediate environment). According to the timeline of events leading up to the death, the discarded hose had been left - with water residue present in the flex/jet heads - in the temperate winter sun, before being used; during the intervening period the bacteria had established itself and was released via spraying. And although this tragic episode took place in a domestic setting, it successfully highlights the mortal dangers of legionella if procedures aren’t put into place, nor individuals more savvy as to the unseen threats. According to the HSE, 90% of outbreaks have their root causes in failures to identify risk or to put in place effective schemes of legionella control to deal with these risks, and the workplace is a hotbed for potential oversights or indeed, lack of education on the subject per se.

Get your peace of mind. Book a legionella risk assessment >

Inadequate Water Tank Insulation Can be Pivotal in Encouraging Growth of Legionnaires’ Disease-causing Bacteria

So, what are we suggesting can be done to flag up the dangers, in our capacity as something of an authority on the subject of legionella control? Well, there are plenty of provisional safeguards that can be taken by business owners from the outset, including ensuring that water cannot stagnate anywhere in the system, courtesy of regular movement of water in all sections of the systems and by keeping pipe lengths as short as possible (and/or removing redundant pipework and known deadlegs). In addition to this, the avoidance of using materials that harbour bacteria and other microorganisms (or provide nutrients for microbial growth) are recommended. Other steps which can be taken to prevent risk of legionella manifesting include downsizing water tanks (to minimise volumes of stored water), installation of delayed action float valves (to reduce volumes in existing tanks), removal of storage where mains supply can match demand, routine repair and refurbishment of all water tank types, utilising hand laid GRP as an alternative means of water tank lining, the alteration of distribution pipework (to create a more balanced cross flow), the isolation of twin tank systems (to reduce overall storage capacity) and the decommissioning (and removal) of redundant tanks, including all associated pipework.

Elsewhere, and other ways in which companies can work towards actively preventing legionella during the summer (by way of supressing temperate gain and maintaining a healthy and compliant water system) can comprise of locating the cold water storage tank in a cool place - and out of direct sunlight - while also ensuring sufficient insulation is present on both the tank and cold pipework. Meanwhile the implementation of a regular flushing regime thus affording a regular turnover of stored water is a given, as is the undertaking of monthly temperature monitoring of sentinel outlets (and representative outlets) on a rotational basis. With regards to this, said outlet needs to be run for a minimum of 2 minutes, after which the temperature should be at a maximum of 20°C. By a similar token, the adhering to six-monthly monitoring of cold water storage tank temperatures is strongly urged.

Naturally some workplaces are considered to offer more in the way of heightened legionella risks than others (healthcare premises, care homes, residential homes, greenhouse farming, horticultural, laboratory analysts, water service providers and maintenance workers (specifically those who are tasked with cleaning/maintenance of cooling towers, air conditioning engineers, plumbers and spa pool cleaners), leisure, hotel industry and cruise ships employees and water spray system-utilising sectors (for instance, humidification in printing works and textile mills). Yet at the end of the day any business which accommodates (and regularly plunders) a water storage system could, potentially be susceptible to the onset of legionella and the medium and long-term implications associated with the manifestation of the infection borne from it, namely Legionnaires’ Disease. Let’s face it, what employer’s premises don’t provide (at the very least) a hot and cold water system in relation to hand hygiene, whilst many are also home to showering facilities and/or air conditioning apparatus in one form or another.

In summary, certain occupations are at an increased risk of exposure to legionella on account of their work activities necessitating a close proximity to a water system, such as those described above. That said – and it’s worth remembering – that if legionella control measures and practices are put into place, risk of exposure remains very low.

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