“It is also important to highlight that the use of nano mist does not replace the requirement for standard surface cleaning.”—A noteworthy extract from the press statement given last week by the Director General of Health Malaysia on the use of disinfectant spray guns as a primary and only surface disinfection method. From only squeeze bottles and dispensing pump bottles sold in the market, disinfectant presentation and release have extensively evolved with technology. To date, existing disinfection technologies include auto-dispensers (no touching!), software-integrated dispensing machines, and of course, the widely marketed and hot topic of this blog: disinfectants that are electrostatically sprayed into the surroundings or, what we call, disinfectant spray guns. Although they might be attractive and possibly a cheaper alternative when compared to other disinfection technologies, can we actually give harmful bacteria or other microorganisms a headshot with these guns?

In this blog, we will discuss the factors to consider when using a disinfectant mist spray gun and our suggestions on the efficacy test required to verify its application.

Factors to Consider When Deciding to Purchase a Disinfectant Spray Gun

Is the active substance of the disinfectant compatible with the disinfectant mist spray gun?

“The ingredient list states that it contains alcohol as its active ingredient. Seems promising, don’t you think, James?”—Disinfectants are often classified as alcohol-based or alcohol-free products. Multiple studies have been done to support the efficacy of alcohol towards coronavirus—at least 60% of alcohol is recommended to kill coronavirus. Although commonly used in disinfectants, alcohol-based disinfectants are highly flammable and may not be suitable to be electronically charged in order to be released through a mist spray gun. But did you know that most of the surface disinfectants used in these mist spray gun are quaternary ammonium compound (QAC)-based or chlorine-based? There are two important aspects that we would like to discuss in this blog: the safety and efficacy of a disinfectant mist spray gun.

Is it safe to be sprayed on humans? Do we need to wear any personal protective equipment (PPE)?

“Hey Natasha, how’s your reading going? Have you reached the part where CDC mentions the safety and effectiveness of a disinfectant product might change based on how we use it?”—We all know too much exposure to certain chemicals, especially those contained in disinfectants, can be harmful towards human health. The route of product exposure also plays a big role towards our health. Disinfectant mist spray guns releases disinfectants into the surroundings as fine mists. In cases of surroundings with poor ventilation, these light weight disinfectant droplets tend to stay longer in the air and are inhaled by those present in the room. Apart from inhalation, these disinfectant mists are also exposed to human via skin, eyes, and even oral ingestion. Long-term exposure towards the disinfectants released from mist spray guns can lead to airway, skin, and eye irritation in humans. Therefore, to minimize human contact towards aerosolized disinfectants, personal protective equipment (PPE) are highly recommended to be worn prior to using the device without any individuals present in the room or area to be disinfected. Once the disinfected area has achieved a good safety level margin of disinfectant exposure, only then it is recommended for others to use or enter the room.

Are the current standard methods sufficient to evaluate the efficacy of a disinfectant mist spray gun?

“Charles, do we really need to do these carrier tests? I think suspension tests would be sufficient, no?”—The efficacy of these surface disinfectants shall be evaluated with a combination of quantitative suspension tests and its suitable quantitative carrier tests. Currently, some of the popular available carrier tests for surface disinfectants are EN 13697, EN 17387, EN 16615, and EN 16777. Read more about them and all our other offered efficacy tests here. If the disinfectant application does not require wiping action after spraying, we would recommend our customers to do EN 13697, whereas EN 16615 is suitable for surface disinfectants that require wiping action after spraying. Although seem suitable to evaluate the disinfectant of a mist spray gun due to the similar mode of application, there is a limitation in using EN 13697 to evaluate the efficacy of a mist spray gun.

In EN 13697, 0.05 mL of bacteria is inoculated on a stainless steel and let dry. After drying, 0.1 mL of surface disinfectant is transferred onto the stainless steel disc, entirely covering the inoculated area. This mimics the real-life application of a surface disinfectant released via trigger spray that completely covers the surface to be disinfected as instructed on the bottle label. In the case of a disinfectant mist spray gun, the disinfectant mist released from the nozzle may not be sufficient to cover the surface intended to disinfect. Other than the small particle size, the volume of disinfectant released per spray per minute may also contribute to this factor. These fine mists are also subjected to evaporate faster when compared to the heavier and bigger disinfectant droplets released via a trigger spray, thus, reducing the surface area of contact leading to lower efficacy of the disinfectant.

What Do The Top Guns Say About These Guns?

“CDC does not either recommend, or not recommend, use of these devices for disinfecting community spaces for COVID-19. EPA does not recommend using these methods to apply disinfectants.”—We presume these claims were made in light of the lack of data that justifies the performance of disinfectant spray guns and its complementary disinfectants.

So, what would be the suitable efficacy testing approach for a disinfectant mist spray gun? We would approach the efficacy testing in three stages as follows:

Stage 1: Quantitative suspension test of the suitable area—such as EN 1276, EN 1650, and EN 14476—to evaluate the efficacy of the surface disinfectant liquid.

Stage 2: Quantitative carrier test of the suitable area—such as EN 13697 and EN 16777—to evaluate the efficacy of the surface disinfectant when in contact with a hard surface.

Stage 3: TECOLAB in-house test method to verify the efficacy of a disinfectant mist spray gun during a real-life application when in contact with a hard non-porous surface or porous surface.

The combination of stages 1 and 2 enables you to prove the efficacy of your surface disinfectant liquid and ease the registration process of your product. Stage 3 verifies the efficacy of your product when used with a mist spray gun and enables you to establish a correct instruction of use for end users. Consult us to know more about our customized in-house test method.