Fogging- A Powerful Disinfecting Layer for Biohygiene?
Updated: Feb 8
By: Nelly Nastase
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), most likely spreads through invisible respiratory droplets created when an infected person coughs or sneezes. Those droplets can be inhaled by nearby people or land on surfaces that others might touch, spreading the infection when they touch their eyes, nose, or mouth (Science, 2020).
There is a lot that is not fully known about the new SARS-CoV-2 virus, like how long does it remain active in the air or on surfaces. According to a recent study, the virus remains in the air for up to 3 hours and approximately 2-3 days on stainless steel and plastic surfaces (Van Doremalen et al, 2020). Another study found that a related SARS-CoV-1 virus that causes SARS can persist up to 9 days on non-porous surfaces such as plastic or stainless steel (Kampf et al, 2020).
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Several reports found that the SARS-CoV-2 virus has been detected in feces, indicating that the virus can spread by people who don’t properly wash their hands after using the bathroom (Wang et al, 2020). However, the CDC says there is no indication that it spreads through drinking water, swimming pools, or hot tubs (CDC, 2020a). The virus has been found to spread less effectively outdoors due to a variety of factors.
Previous research on the relationship between respiratory-borne infectious diseases and temperature have indicated that the ability of SARS and influenza viruses to spread decreased with increasing temperature (Jaakkola et al, 2014; Chan et al, 2011). The underlying hypothesis includes higher vitamin D levels, resulting in better immune responses (Aranow, 2011); increased UV radiation; and school holidays in the summer. Reports of correlation between respiratory diseases and the levels of UV radiation have also been considered, and previous studies have reported that high levels of UV exposure can reduce the spread of SARS-CoV virus (Duan et al, 2003).
However, according to the current results, the cumulative incidence rate and R0 of COVID-19 holds no significant association with ambient temperature, suggesting that ambient temperature has no significant impact on the transmission of SARS-CoV-2 (Yao et al, 2020). This is similar to the Middle East respiratory syndrome (MERS) epidemic, where the MERS coronavirus continued to spread even at temperatures of around 45°C (Alshukairi et al, 2018).
Measures to minimize airborne transmission of COVID-19 indoors include sufficient and effective ventilation, possibly enhanced by particle filtration and air disinfection, avoiding air recirculation, and avoiding overcrowding (Morawska et al, 2020).
Fogging is a deep cleaning method that has been used in hospitals for dealing with MRSA. Fogging uses an antiviral disinfectant solution to clean and sanitize large areas of a building quickly and effectively by spraying a fine mist from a spray gun, which is then left to evaporate, usually for less than an hour. It can kill off viruses and other biological agents in the air and on surfaces. The task requires full protection from the sprayed chemicals. The product used is safe on electronics and other equipment as the mist is exceptionally fine to penetrate all areas to kill off the virus effectively.
Fogging should be conducted only using products whose product label specifically includes disinfection directions for fogging, fumigation, or wide-area spraying. It means that the product’s safety and efficacy have been evaluated by the EPA, specifically for fogging. Otherwise, the product might not be effective in disinfecting surfaces by fogging (EPA.gov, 2020a). The EPA has been expediting applications to add directions for use with electrostatic sprayers to products intended to kill SARS-CoV-2 (EPA.gov, 2020b).
Wet or chemical fogging employs a fine mist of disinfectant solution which remains on surfaces for several hours until it evaporates. Dry fogging, on the other hand, uses smoke to treat the area, leaving no chemical trace behind. The main advantages of fogging are the ability to cover large areas quickly and effectively; the ability to reach areas difficult to clean using other techniques. It eliminates pathogens in the air and on all surfaces, including furniture, walls, and ceilings.
The downsides are that it requires a thorough cleaning in advance as dirt and other materials might cover parts of a surface, protecting it from the effects of the biocide spread by fogging; the chemicals used are often more expensive than other disinfectants, and the required amount depends on the size of the space that is being disinfected. However, fogging is cost-effective because it allows the rapid disinfection of large areas with minimal disruption.
Ultraviolet (UV) radiation can be used for non-contact disinfection, where UV-C light is used to kill or inactivate pathogens by damaging their DNA or destroying nucleic acids. UV disinfection is commonly used to treat water – its advantages are lack of chemical agent, ease of use, and low economic cost. The lack of chemical agent means that UV disinfection can be used as often as needed, without any fear of long-term consequences for the operator or the client.
However, UV disinfection requires a direct impact of UV radiation for some time – if the light shines indirectly, or is obscured by dirt or something else, the disinfecting effect is lost. Also, prolonged exposure to UV light can be harmful to humans – skin exposure can produce sunburn and skin cancer. In addition, eye exposure can damage the cornea or, in rare cases, the retina, leading to temporary or permanent vision impairment or even blindness. The risk is compounded by the fact that UV light is invisible to the human eye. Therefore, the operation of UV disinfection equipment requires caution.