Most household liquid bleach contain 5% to 7% of a corrosive chemical substance called sodium hypochlorite. At this concentration, the chemical can be irritating to the skin and eyes so extra care must be taken to dilute the bleach for surface disinfection purposes.
It may seem counterintuitive to add a large amount of water to a small quantity of bleach. However, a proper dilution of liquid bleach is crucial: Scientific evidence has shown that bleach is more effective at killing germs when diluted than using it straight out of the bottle.
The recommended ratio is 20ml of bleach to 1 litre of water. Use a plastic measuring cup and container as the corrosive chemicals in bleach will react with metal. When diluting the bleach, you must ensure the area is well ventilated and you must wear gloves and a mask or goggles. Accidental exposure to bleach, even the diluted version, may cause cough and irritate eyes and skin.
Bleach is reactive to heat so do not use hot water or water from a hot tap for the dilution. Most importantly, use only water for the dilution. Do not mix the diluted bleach with other detergents or ingredients such as floor cleaner and vinegar, as it might trigger the release of toxic gases from chemical reactions. The content and ingredients of various liquid disinfectants are different and should not be mixed.
When cleaning with the solution, try to have at least one minute of contact time between the solution and the surface. To establish good contact, use a cloth that is saturated enough to allow the surface you’re treating to remain visibly wet for at least one minute.
Diluted bleach should be used only on inert and hard surfaces; it should not be used on metal, painted surfaces or sofas or leather goods. It is important to ensure proper ventilation during and after cleaning using the diluted bleach.
Bleach decomposes over time. Once diluted, it is best used within 24 hours. Therefore, dilute only what you need for each daily use. Likewise, the concentrated bleach can decompose, especially upon exposure to heat or sunlight. Store the opened bleach container in a dark and cool place that is not accessible to younger children. The effective shelf-life of an opened container of liquid household bleach is three months.
You should also avoid discarding any unused diluted bleach solution directly into a toilet bowl or kitchen sink. As mentioned above, the bleach could mix badly with ingredients left in sink drains and pipes. It would also destroy the beneficial bacteria that exist in the sewage system.
Preparing your own disinfectant from bleach might seem easy but you must note and follow the precautionary steps to avoid accidental exposure to the harmful effects of bleach.
Diluted bleach is not intended for human use and must not be used to sanitise hands. If you encounter any symptoms such as cough, irritation and pain when dealing with bleach, seek medical attention immediately.
GOH CHOON FU & LONG CHIAU MING
Note: Goh is senior lecturer and researcher, Skin Research Group, School of Pharmaceutical Sciences, Universiti Sains Malaysia; Long is associate professor, PAP Rashidah Sa’adatul Bolkiah Institute of Health Sciences, Universiti Brunei Darussalam, Brunei Darussalam
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