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Electrostatic Sprayers, Fine Misting and ULV Foggers

Which to Use When, Where and with What Products


There are three popular portable equipment mechanisms being used in janitorial services for the delivery of products designed to improve surface hygiene:

  • Handheld/Backpack Electrostatic Sprayers (Emist, Victory and Protexus)
  • Insitu Fine Misting/Fogging Whole Room Systems (HaloMist)
  • ULV Foggers (Longray, B&G)


Electrostatic Sprayer Application of Disinfectants

Electrostatic Spraying equipment has emerged as the ‘new next best thing’ on the custodial equipment market over the past three years. But the question remains: Is it as much of a qualitative improvement as its proponents claim?



The process was originally referred to as electrostatic coating and was developed for use in manufacturing processes such as automobile painting. By electrically charging small droplet size coatings, such as paint, a more even application could be achieved, and electrically charged droplets would be drawn to adhere to the obscured far side of surfaces being treated. Further benefits included less product with a faster application.


The key to the development and adoption of this technology was how it helped liquid products, such as paints, that had no natural adhesion qualities when wet, adhere to vertical surfaces for long enough to bond during the drying process.


The technology then spread into horticulture, for both outdoor and indoor grow environments. The electrostatically charged droplets enabled product to be easily applied to both the upper and under sides of the foliage, reducing the amount of product used.


In commercial cleaning it claims a better delivery of disinfectant products to surfaces, especially vertical surfaces to which the disinfectants have no natural ability to adhere. Such equipment, when applying disinfectants, should only be used when the applicator is using appropriate Personal Protection Equipment (PPE). It should also only be used when there are no other people in the immediate area.


There are some limitations to consider:

  • Disinfectants applied via such a spray technology require a droplet size of 80 microns or larger to meet OSHA requirements.
  • Even at this relatively large droplet size, disinfectants tend to dry out in two to three minutes, which is short of the vast majority of product label stated dwell times, which range from five to ten minutes (disinfectants provide no ongoing cleaning or protection once they dry out).


Consequently, some have questioned the efficacy of disinfectants when applied via such methods. However, research has indicated that 50% of the effective ‘kill rate’ of some surface disinfectants occurs within the first 60 to 90 seconds of surface contact time.



This leads to other questions about stated ‘kill rates’ of disinfectants and how applicable they are to ‘real world’ usage. Stated ‘kill rates’ are based on lab testing environments, where there is no biofilm present.


The CDC acknowledges biofilm inhibits disinfectants reaching pathogen cell walls, and so impacts the efficacy of such products, as disinfectants do not fully address biofilm. As biofilm is almost universally present on indoor surfaces, the implication is that the stated ‘kill claims’ on disinfectant labels may not be as high as results achieved when used in everyday applications.


For these reasons, the effective dwell times when applying disinfectants with electrostatic sprayers will likely be less than what is stated on product labels. So, although it may be a technically effective means of application, the results may not be ‘as advertised.’ What, then, are the alternatives?


Fine Misting/Fogging Whole Room Systems

Whole room fine misting/fogging systems have been gaining traction, especially in the health care space, delivering products such as hydrogen peroxide. Devices are wheeled into the room which is then sealed off while the unit fills the room with a fine mist of hydrogen peroxide.


This equipment delivers a one micro droplet sized mist into the enclosed space. This process involves filling the enclosed room with this fine fog, which may take several hours. People and animals cannot be present during the application.


With this process, the hydrogen peroxide mist will reach all areas of the room, areas that conventional ‘spray & wipe’ protocols may miss (electrostatic spraying only impacts surfaces they are directed to).


An advantage of whole room misting is the disinfectant may have greater surface contact dwell time.


An advantage of whole room misting is the disinfectant may have greater surface contact dwell time. However, all surface disinfection products provide relatively poor soil removal (including biofilm), and no residual cleaning or protection once they dry out. Surface areas that are missed with such products also remain pockets of contamination that support rapid surface repopulation by pathogens.


ULV Foggers

Another product application method is ULV (Ultra Low Volume) Foggers. ULV Foggers deliver product at droplet sizes ranging from 10 microns to 120 microns. For this reason, ULV Foggers should only be used with products that are safe for use in the presence of people when adjusted to levels below 80 microns. Unlike electrostatic sprayers which are directional and surface specific, ULV Foggers treat entire areas.


In janitorial applications they are used with probiotic cleaners, which are safe to be delivered into the atmosphere at between 10 to 20 microns droplet sizes and require no PPE. Probiotic cleaners comprise natural probiotic bacteria which have a natural ability to adhere to virtually any surface, in any position (unlike disinfectants).


Probiotic cleaning agents differ to chemical disinfectants in other ways:

  • They continue working whether wet or dry.
  • They provide ongoing cleaning.
  • They provide ongoing protection against surface re-population by unwanted pathogens.
  • The probiotic bacteria have the capacity to move across surfaces.
  • They are pH neutral and will not harm surfaces.
  • They comprise US EPA ‘Safer Choice’ delivery surfactants and US FDA GRAS schedule probiotic bacteria, and so are safe for use in the presence of people and animals.
  • They are more effective at addressing biological surface contamination.


Probiotic cleaners can be effectively applied with electrostatic sprayers, but that technology is not necessary with these products given the natural ability of the probiotic bacteria to adhere to surfaces.



The choice of equipment is largely determined by the products being used. Electrostatic sprayers help conventional chemistry products to adhere to surfaces they normally would not adhere to, and so improve the efficacy of those products. They are fast, easy to use, but relatively expensive, ranging from between several hundred dollars to several thousand, depending on make and model. When used with toxic disinfectant chemistry, they should be used at 80 microns droplet size or larger to meet OSHA health requirements, which implies heavier product usage.


Fine misting machines that deliver one micron droplet size ultrafine mists of disinfectant products can only be used in sealed off, unoccupied spaces. Their advantages over electrostatic sprayers is the delivery of product to surface area which is not usually accessible to applicators using electrostatic sprayers, as well as the provision of longer surface exposure. Use of this equipment needs to be scheduled and can take longer to disinfect an area as well. These devices are also expensive and can cost several thousand dollars.


ULV Foggers are best used with non-toxic products, such as probiotic cleaners. Probiotic bacteria have a natural ability to adhere to virtually all surfaces, and so do not need to be electrostatically enhanced. ULV Foggers that can populate open areas can also be directed to surfaces. They are ideal for use with probiotic cleaners at small droplet sizes of between 10 and 20 microns, which is more economical in terms of product usage. ULV Fogging units are the lowest cost delivery mechanism, with most ranging between two to three hundred dollars.


By Ed Celaya, President, K-12 Specialties & Exact Science Facility Solutions