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  • Josie L. Turpin

Dwell times | Does your anti-bacterial spray work?

We've all seen the adverts, "just one spray and wipe away - kills 99% of bacteria" but are the cover labels misleading us?


Aside from the obvious fact that these sprays are 'anti-bacterial' and as such only work on bacteria (not viruses), the answer is YES as they neglect to mention a key piece of information which is usually hidden in the small print on the back of the label - Dwell Time.

The difference between AIR at 5-log and most bacterial sanitisers at 3-log is that 5-log means that AIR is 100 times more effective against ALL viruses and bacteria.

Dwell Time (only applies to solutions)

This is the length of time that a solution needs to be in contact with a surface for it to have the claimed kill rate shown on the front of the bottle – in other words, it’s the speed of kill.

When you spray a tabletop with a solution, the 'dwell time' is how long the solution actually needs to be left before wiping off; 1 minute, 5 minutes or even longer

To achieve the performance claim of a disinfectant spray, for example 99%, a solution often needs to be left for 30-seconds, a minute, five minutes or maybe even longer for this to be achieved.

I would read the back of a few disinfectant supplies in your home – you might be surprised.

Let’s think about what this means in a restaurant setting

Once a table sitting has finished and the clear up takes place ahead of the next customer, the employee has to remove all dirty plates, cutlery and glasses. Before the table can be re-laid, it then needs to be cleaned with a sanitiser. This is normally done in real time with a spray and wipe so there’s a quick turnaround and service can resume – just think about fast food chains where the restaurant’s performance is so heavily based on the turnaround of its customers.


Unfortunately, this doesn’t take into account the dwell time of a sanitiser to achieve the claimed log reduction. So, in reality the solution would need to be left a minute, five minutes or longer, and that’s likely to be shown on the back of the bottle or in the solution’s technical reports.


But, what does this actually mean?

If a solution has a combination of, say, a 99% kill rate and needs a five-minute dwell time to achieve this, then that’s certainly not ideal. This means to be effective in a cleaning regime, the cleaner would have to spray a surface, wait for five minutes, and then still have 10,000 virus cells out of the one million left viable.


Some examples from my cleaning cupboard, good job I have an AIR in my house:

Log reductions and kill rates

For example, from a small colony of a million viruses on a restaurant table, a 1-log or 90% kill rate will leave 100,000 microbes behind. This table shows the various connotations:

Log, percentage and remaining bacteria from a small colony of 1m microbes.


Let’s look at this another way. The difference between 4-log and 3-log is that 4-log is 10 times more effective and leaves behind 10 times less microbes than 3-log. The difference between 5-log and 3-log is that 5-log is 100 times more effective. The difference between 5-log and 1-log is 10,000 times more effective. This shows just how quickly the logarithmic scale ramps up.


The difference between AIR at 5-log and most bacterial sanitisers at 3-log is that 5-log means that AIR is 100 times more effective against ALL viruses and bacteria.

AIR can be purchased online by visting https://www.atmos-clear.com/air-uk-buy-now.html


If you have any questions about AIR, please email sales@atmos-clear.com






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