Purchasing and Using Multipurpose Disinfectant Sprays – Facts Unpacked

1.Some hypochlorous acid disinfectant products yielded similar test results as alcohol-based preparation and diluted bleach solution. Is it recommended to replace these 2 traditional disinfectants with hypochlorous acid disinfectant sprays?

The fact is that alcohol-based preparation and diluted bleach solution have long-established scientific research data to support their disinfecting efficacies. In this test, these 2 common disinfectants have shown satisfactory bactericidal efficacies in an environment with a high level of interfering substances and within a short period, and also performed well at eliminating Adenovirus. This shows that they are ideal choices for disinfecting hands and the environment respectively.

Despite the fact that some models of hypochlorous acid disinfectant products, when the samples were freshly opened, performed to satisfaction in killing bacteria and reducing viral infectivity, the various models of hypochlorous acid disinfectant products in fact showed huge disparity in performance during the test. In addition, the active ingredients of hypochlorous acid disinfectant products are unstable, so it is questionable whether they can maintain the ideal bactericidal and virucidal efficacies over an extended period of use.

According to the results of the stability test conducted by the Council, some hypochlorous acid disinfectant products showed a drastic drop in available chlorine concentration on the 14^th day of continued simulated use and storage, and the available chlorine concentration directly impacts the bactericidal efficacy and reduction of viral infectivity. As such, the Council advises consumers to properly store and use hypochlorous acid disinfectant products as soon as possible once the product has been unsealed.

2.Why is it important to take note of the manufacturing date of hypochlorous acid / chlorine dioxide products?

It is recommended to pay attention to the manufacturing date should you need to purchase hypochlorous acid / chlorine dioxide products, as “freshly” manufactured products and a proper storage environment are crucial. The active ingredient concentration of hypochlorous acid and chlorine dioxide products may decrease over time. For example, if a product has already been in storage for a few months at the time of purchase, its active ingredient might be significantly different from when it was fresh out of production. At the same time, pay heed to the environment in which the product was stored before purchasing. Avoid buying items which have been placed under a spotlight or near a heat source.

The Council found that some hypochlorous acid / chlorine dioxide products did not clearly label the product manufacturing date, nor provide any information on the expiry date. Consumers should refrain from buying disinfectant products that lack clearly labelled information of the effective period. 

3.Why should hypochlorous acid products be used as soon as possible after opening?

Although some hypochlorous acid products claim an effective period of 3 to 6 months after opening, the Council’s stability test results revealed that some hypochlorous acid disinfectant samples’ available chlorine concentration had significantly dropped after 14 days of simulated use and storage during the test period.

Research from Japan also pointed out that the active ingredients of hypochlorous acid solution (acidic) markedly dropped after opening, using and storing for 2 to 4 weeks. In the same research, the available chlorine concentration of opened hypochlorous acid solution samples had dropped to such an extremely low level that was barely effective in eliminating the test viruses.

Based on the results of the stability test conducted by the Council, some hypochlorous acid disinfectant products showed a significant decrease in available chlorine concentration on the 14^th day of continued simulated use and storage. As such, the Council advises consumers to use hypochlorous acid disinfectant products as soon as possible (preferably within 2 weeks) once the product has been unsealed, before all the active ingredients have completely disintegrated, rendering the product ineffective at killing bacteria and reducing viral infectivity. The Council also advises against hoarding large amounts of hypochlorous acid disinfectant products or purchasing bulk-sized products.

4.How should I select hypochlorous acid disinfectant products?

Besides noting information such as the manufacturing date and effective period of hypochlorous acid disinfectant products, consumers are also advised to peruse the product’s active ingredient concentration.

A research from Japan indicates that hypochlorous acid solution (acidic) must contain a certain level of available chlorine in order to be effective against the novel coronavirus. The research emphasises that regardless of the preparation method of the hypochlorous acid solution, the available chlorine concentration must be at least 35ppm to be effective. For products made from sodium dichloroisocyanurate (NaDCC), the available chlorine concentration must be at 100ppm or above.

Based on the Council’s test results, hypochlorous acid disinfectant models with available chlorine concentrations of 100mg/L (equivalent to 100ppm) or above, generally had a more satisfactory overall performance.

However, the test found that some models’ available chlorine concentration was lower than claimed or labelled. The Council recommends product suppliers to check the stability of the active ingredients as well as ensure the labelling information (including the active ingredient concentration) is accurate.

On the other hand, consumers should pay heed to whether the product provides correct directions of use (such as removing the dirt on the objects’ surface prior to applying the disinfectant), or suggested use amount and effective time. Otherwise, it will increase the chance of consumers misusing the product.

5.What is the correct way of using hypochlorous acid disinfectant products?

Despite certain hypochlorous acid disinfectant models showing satisfactory bactericidal efficacy and reduction of viral infectivity in this test, consumers should bear in mind that the products can only achieve the desired virucidal effect when used properly. Inappropriate usage of the products may result in lowered guard due to a false sense of security, which may conversely increase the risk of virus infection.

On summarising research data and information from international health organisations, currently the more affirmed use of hypochlorous acid is for disinfecting the surface of objects. Research from overseas pointed out that for hypochlorous acid solution to effectively deal with the novel coronavirus, dirt (such as organic substances) on the surface of the object should first be removed, then a sufficient amount of disinfectant should be applied in order to effectively eliminate the virus on the object’s surface. Too little disinfectant would not be enough to take effect.

Follow the steps below to clean and disinfect objects likely to be contaminated with pathogens:

Step 1 — Cleaning: The prerequisite to effective and satisfactory disinfecting result is to first clean properly, to maximise the efficacy of the disinfectant. It is recommended to use cleaning detergents and water to remove the dirt on the object’s surface using a rubbing motion, followed by disinfecting procedures.

Step 2 — Disinfecting:

• Pay attention to the product’s instructions of use: Check the applicable environment, materials and surface type (e.g. a hard and smooth surface or a porous surface) as suggested for the product;
• Note the suggested product effective time: Ensure the surface of the object to be disinfected stays damp during the effective period;
• Spray a sufficient amount of disinfectant so that the surface of the object is completely soaked, then allow enough time for the disinfectant to be in contact with the object’s surface (ideally over 5 minutes). Alternatively, repeated rub the surface to achieve maximum disinfecting effect. For objects deemed more likely to be contaminated, it is advised to extend the effective duration of the disinfectant, and/or increase the amount or concentration of disinfectant used.

The Council wishes to emphasise that the product’s bactericidal efficacy and reduction of viral infectivity can only be fully achieved with proper use. Improper usage of the products may result in lowered guard due to a false sense of security, which may conversely increase the risk of virus infection.

6.Can disinfectants be sprayed directly at the human body?

Under any circumstances, it is not recommended to spray disinfectants directly at the human body. Doing so does not lower the risk of a virus carrier spreading the virus via respiratory droplets or through body contact. Spraying disinfectants containing chlorine or other toxic chemical substances directly at the human body may irritate the eyes and skin. If inhaled, it may cause bronchospasm, or gastrointestinal tract problems such as nausea and vomiting.

pH values of certain disinfectant spray samples leaned towards highly acidic or more alkaline. If a disinfectant spray’s pH value is too extreme (too acidic or too alkaline), it may irritate the skin through contact. Daily and long-term contact with strong acid and strong alkaline substances may pose a higher risk of skin irritation to those with sensitive or delicate skin, such as children. Moreover, products containing allergenic fragrance and preservatives, or surfactants commonly found in cleaning products, may have a higher chance of irritating the skin, eyes and respiratory tract.

Although many products claim to be safe, consumers should still avoid breathing in large amounts of the disinfectant sprays during use. Should any respiratory tract, eye or skin irritation or allergic reaction occur after using or coming into contact with any disinfectants, such as nasal burning, coughing, watering eyes and itchy skin, and if such reactions subside after discontinued use of the disinfect, then it is likely that the reaction was caused by the disinfectant and the product should no longer be used. If there are asthma patients, children and elderly in the household, it is even more important to select and use disinfectants with caution.

7.Can disinfectants be used to disinfect air in a confined space?

If the disinfectant is indirectly sprayed onto objects’ surface through spraying into the air, viruses on the surface of objects may only come into contact with a very small amount of disinfectant due to spraying from a distance, and if the disinfectant amount is too low or the available concentration is too low, disinfection efficacy may not be significant. On the other hand, the use of atomisers to vapourise any kind of disinfecting gas is not likely effective in achieving the desired anti-pandemic efficacy, it may also result in wastage as well as causing health impacts to those in the premises. It may also contaminate food and beverages, increasing the risk of consuming the disinfectant or its residue by accident.

8.Should hypochlorous acid disinfectants be used for disinfecting hands？

In March last year, the Taiwan Centers for Disease Control released an anti-pandemic promotional material stating that hypochlorous acid is suitable for general disinfection but not recommended for use on the human body. The Centers stressed the hypochlorous acid has a poor stability as well as a short shelf life, thus its efficacy may drop after being stored for a long period of time. It also disintegrates easily under sunlight and therefore should be stored in an opaque container. The Centers recommends washing hands with soap as the most ideal way to clean our hands or by using 75% alcohol-based preparation when it is inconvenient to wash your hands. Both methods are correct anti-pandemic measures.

9.What are the flaws in alcohol-based preparation and diluted bleach solution？Any precautions we should pay heed to when using them?

In a real-life environment, diluted bleach solution cannot be used for disinfecting the skin and may not be suitable for metal surfaces. Diluted bleach solution should be used within 24 hours, and it is advised to wear rubber gloves when using diluted bleach to protect your skin.

On the other hand, alcohol-based preparation is generally used for disinfecting hands yet may cause dry skin or temporary irritation. You may choose alcohol-based preparation products with added moisturising content (like glycerin) or apply hand creams regularly to relieve dry skin. In addition, although alcohol-based preparation could be used to disinfect objects’ surface, you should use with care due to its flammability and keep it away from naked flames when in use.

The disinfection efficacy of alcohol-based preparation and diluted bleach solution has long been proved by scientific evidence as a reliable choice. If they are replaced by disinfectant products with questionable efficacy, this might increase the risk of virus infection and defeat its purpose.

10.What should I do if alcohol-based preparation and diluted bleach solution could not be used under certain situations？

In fact, cleaning objects with detergents is an effective way to reduce the virus count on the surface of objects.

Smooth and non-porous surfaces, such as glass, metal, or plastic, could be wiped with a damp cloth with detergent and water, while clothing and other textiles are recommended to be soaked and washed by detergent. The more often an object is used, the more frequently you should clean or disinfect the object.

For further details, please click Questions about the methods and test conditions adopted for the test on multi-purpose disinfectants