[Important note for Epidemic Prevention] How to use bleach properly: 8 trivia you need to know.

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Bleach is a must-have disinfectant at home. The main ingredient of bleach is sodium hypochlorite, which can degrade the protein of microorganisms, thereby killing bacteria, fungi and viruses. Bleach was sold out during the outbreak of Coronavirus. However, if you don’t use it properly, blech can be ineffective. Here is the 8 trivia you need to know.

Notes before cleaning

【防疫必讀】漂白水使用教學:8個冷知識 當中一個令漂白水無效!

1.Bleach can expire

Some people may have hoarded a large amount of bleach. However, bleach can expire! Sodium hypochlorite, the bactericidal ingredient, is actually unstable and can decompose over time. Although some formulations will include stabilizers to reduce the rate of decomposition, the Consumer Council recommends that the public should use up within 3 years.

2.Different degrees of dilution of bleach

The sodium hypochlorite concentration in household bleach is generally 5.25%. The Department of Health indicates that the dilution concentrations of bleach should be in 1:99 or 1:49. However, there are some bleaches with sodium hypochlorite below 5.25% on the market, so customers have to pay attention to the label when buying. 

Take bleach containing 5.25% sodium hypochlorite as an example. 1:99 diluted bleach is suitable for general household cleaning and disinfection. And 1:49 diluted bleach is used to disinfect surfaces or objects contaminated with vomitus, faeces or secretions.

If you purchased the bleach that is less than 5.25% sodium hypochlorite, you can adjust it according to the following calculation method:

Adjust the amount of bleach = 5.25 ÷ sodium hypochlorite concentration of bleach 

For example: if bleach contains 5% of sodium hypochlorite, the “calculation method” is 5.25 ÷ 5 = 1.05 times. That is, use 10 ml x 1.05 = 10.5 ml bleach to adjust the concentration.

3.Danger of bleach

Undiluted bleach releases toxic gases under the sun, so bleach must be stored in a cool, shaded and out of reach of children. In addition, bleach will irritate the mucous membrane, skin and respiratory tract, so you must wear masks, gloves and other equipment when using, and dilute and use in a place with air circulation.

Notes to take during cleaning

【防疫必讀】漂白水使用教學:8個冷知識 當中一個令漂白水無效!

4.Way to dilute bleach: Do not use hot water

Many people use bottle caps as a measurement to dilute bleach. However, different brands have different amount in bottle caps, the dilution amount will become inaccurate. Therefore, you should measure the capacity of the bottle cap first to ensure the correct dilution amount. It is more appropriate to use a spoon or measuring cup to accurately measure the amount of bleach. Remember to use cold water to dilute the bleach. Otherwise, the hot water will break down the ingredients and make bleach lose its effectiveness.

5.Mixing other cleaning products may not improve the performance

Mixing bleach with other cleaning agents may not improve the cleaning power, and the chemical reaction will reduce the bleach’s oxidation ability that loses the sterilizing function. Toxic gases will be generated if acid cleaners or toilet cleaners are mixed with bleach! If a cleaning agent is necessary, wash it with water before disinfecting it with bleach.

6.Undiluted bleach has stronger disinfecting power?

Never pour undiluted bleach directly into the ditch, as bleach is corrosive and therefore metal pipes may leak.

7.Materials that cannot be cleaned with bleach

Avoid using bleach on metal, wool, nylon, silk, dyed fabrics and painted surfaces, except for stainless steel. Bleach should not be used to wipe metal or soak metal products.

8.Use diluted bleach immediately

Diluted bleach should be used within 24 hours because sodium hypochlorite will decompose over time. Pre-diluted bleach will only reduce its cleaning power.


(Source: Consumer Council, Department of Health)

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