Understanding the four elements of effective handwashing
Handwashing looks simple. Soap, water, a bit of rubbing, done! But an effective wash is made up of several distinct elements and getting soap and water onto your hands doesn't guarantee any of them are happening properly. The contamination has to actually come off and the hygiene chemistry has to actually reach the areas where microorganisms are hiding.
Hand washing can be broken into four elements: surface preparation, coverage, dosing and dwell time. If one of them is poorly controlled, it drags the rest of the process down with it, however good the other three are.
1. Surface preparation
This means getting the visible and invisible contamination off the skin - dirt, grease, food residue, whatever's been picked up during the shift. This matters because leftover contamination shields whatever is underneath it from the sanitising chemical that comes after, so no amount of sanitiser fixes a wash that skipped this stage properly. Until that is loosened and washed away, the surface isn't ready for the next stage.
The same principles from Sinner's Circle apply: time, temperature, chemical action and mechanical action. For handwashing, mechanical action mostly comes from rubbing the hands together, soap or detergent supplies the chemical action and water loosens contamination and carries it off. Warmer water can help shift greasy residue, though it needs to stay at a temperature people can tolerate - too hot and it puts people off washing properly and repeated exposure can irritate skin over time.
2. Coverage
Every part of the hand needs to be reached and palms are the easy bit. Fingertips, thumbs, nail beds, the backs of the hands, the gaps between fingers are where contamination tends to sit when a wash doesn't reach properly.
Coverage is hard to control in a manual wash because it comes down to technique and technique varies person to person and wash to wash. Even with training, there's no guarantee the full method gets followed every time. The layout of the station, how the product is applied and the washing action itself all shape how much of the hand actually gets treated.
Where the wash extends to wrists or forearms, the equipment has to treat that as part of the same process. A system built only for hands can't be assumed to cover anything further up the arm.
3. Dosing
Cleaning and sanitising chemicals need to be delivered at the right concentration. Too little and the wash falls short; too much and you're burning through chemical you don't need and potentially leaving residue behind.
Dosing depends on how much concentrate is used, how much water it's mixed with and how accurately that mixing happens - if any of that shifts wash to wash, so does the strength of what's landing on people's hands. Manual dispensing puts the dose in the hands of whoever's washing, quite literally: one person under-doses, the next over-does it. Pumps and proportioning systems take that variability out by delivering a fixed quantity or a fixed mixing ratio.
The correct dose depends on the chemistry and the manufacturer's instructions and there's no single setting that suits every product. It’s also necessary to check on empty containers, blocked lines, worn parts or an incorrect setting as they can throw the dose off even when everything else looks fine.
4. Dwell time
Chemicals need time in contact with the skin to work. Applying them and rinsing them straight off means they haven't had the chance to loosen contamination or bring microorganisms down to the required level. Dwell time comes from the manufacturer's instructions and whatever performance the process needs - longer isn't automatically better and cycles that run on too long just hold people up without improving the result.
People wash at different speeds and the same person will rush it when they're distracted or in a hurry. A clock or a sign can tell people how long to wash for. It can't make them do it.
Worth being clear on what counts, too: walking up to the station, dispensing soap, rinsing afterwards - none of that is dwell time. Only the actual contact period is.
Putting it together
The four elements of handwashing lean on each other, so it's rarely just one thing going wrong when a wash falls short. More chemical won't fix an area that got missed. Longer dwell time won't make up for poor surface preparation. Thorough coverage doesn't count for much if the chemical's too weak or gets rinsed off before it's had time to work.
None of the four is optional and none of them compensates for the others. An effective wash needs surface preparation, coverage, dosing and dwell time all working together, not four separate things to get right on their own.
Learn about Meritech's CleanTech automated handwashing stations here.