Back to resources 6 June 2021 Industry information

ULV Fogging

Ultra-Low Volume (ULV) Fogging is the use of appliances that release liquid (usually disinfectant or pesticides) in a fine mist to cover all surfaces. Because the mist is released under pressure, the liquid spreads across a wide area and can get into those hard to reach places.

Why is ULV fogging effective?

ULV fogging is one of the fastest and most effective ways to sanitise any area, as it is the process of using large volumes of air at low pressure to transform liquids into tiny droplets that are dispersed into the atmosphere, it is perfect for the application of pesticides, sterilisers, and disinfectants.

ULV fogging droplets can range anywhere between 5 – 50 microns, and thus because of this size, they can reach areas and disinfect them more efficiently than standard methods, i.e. spray bottles. Moreover, because of the droplet size, the liquid evaporates much faster, meaning quicker drying times.

What is Ultra-low Volume (ULV) application?

The terms used to describe the amount of liquid applied include high volume (HV), very low volume (VLV), and ultra-low volume (ULV). The quantity applied depends on the desired surface coverage by droplets and the size of the droplets. The concentration of some disinfectants can be high, and they can be applied as a concentrate (undiluted) at ultra-low volume to surfaces. Droplets of around 8 to 10 microns are usually considered to be ULV, but this definition is variable.

What is contact time and the evaporation of droplets?

Contact time or dwell time is the amount of time a disinfecting agent needs to be on a surface to kill the exposed microorganisms. Contact times are between 30 seconds and 15 minutes. Modern disinfectants dry on a surface in less than 5 minutes and reach their peak in efficacy 60 seconds after deposition. The lifetime of droplets on surfaces must match the required contact time on the product label. Research has demonstrated significant microbial reduction with contact times of 30 to 60 seconds. Factors that influence droplet lifetime are size, surface contact, and environmental conditions surrounding the droplet.

Why does the droplet size matter?

The large surface to volume ratio of small droplets results in faster evaporation than large droplets. Evaporation is a function of vaporisation and small droplets lose volume quickly due to their size. The lifetime of a 100-micron droplet is about 10 times that of a 30-micron droplet. After contact with the treatment surface, droplet size decreases with the onset of evaporation. On upward-facing surfaces droplets become flat and the surface absorbs heat and evaporation increases.

What are microns?

A micron is a unit of measurement equivalent to one-millionth of a metre or one-thousandth of a millimetre. Microns are also known as micrometres. The droplets released from the Hurricane fogger range from around 40 to 70 microns.