Sprayers, foggers and backpack pumps

Written by Graziano Dassi on .


A look at the operational potential of some of the technical resources currently on the market

Disinfecting, disinfesting... time passes. Slowly but surely, product catalogues are becoming richer and fuller. Some even go so far as to use bucolic images to stress the chemical industry’s concern for the environment. The trend seems to be for refined formulas and micro doses typical of homeopathy. And the engineering industry? Definitely not lagging behind. This is proved by the fact that the control systems in the equipment are increasingly precise enough to allow the aforementioned tendency to homeopathy (who can forget the adulticide tests in a popular tourist resort in the south of France where 90% of all mosquitoes were eliminated by distributing a specific MD that, after monitoring and testing, found that only one gram of active principle was needed per hectare, i.e. 10,000 square metres). If this is the trend, and fortunately there’s no evidence to the contrary, we must invest in the system: operator, products and equipment. If it is true, and we have no reason to refute this, that man comes before and after statistics, we should all make the effort to inform, educate and motivate so that the code of ethics in our profession leads us towards a system of care for the environment that, on the one hand, protects health and hygiene and respects the ecosystem on the other. I like to quote the slogan of an old company: “good with the good and bad with the bad.” In my opinion, this provides the right idea of our sector’s mission.


I feel a sort of decalogue (ten basic rules) is needed when using any equipment capable of distributing future biocides, i.e. medical devices (MD).

1: user instructions

Consistent with safety guidelines, the instruction booklet must be read. This is not a legal document, such as the Law Decree concerning MDs, but is a technical document that all operators must read before using the equipment. Otherwise, how can he prove that he has been properly informed and trained in the unhappy event of an accident?

2: performance

After studying the characteristics of the equipment, technicians should practice using the equipment. The parameters here are the speed, the flow-rate (i.e. how much product is dispensed per unit of time) and the physical-chemical characteristics of the micro drop.

3: crawling insects and backpack pumps

The simplest example is the use of a backpack pump. Deceptively simple equipment, but with great potential. When dealing with crawling insects, it is difficult to apply a dose expressed as 10 litres/100m2: it is easier if we translate this into 100 ml/m2 (test it and see: an obvious water film appears on the surface). If, on the other hand, the recommended dose is 10 litres/200m2 , then this becomes 50 ml/m2 (the surface is barely moist: this dose is particularly well suited for vertical surfaces). A trivial consideration you may say, but if we use 10 litres/200m2 then we will get the same amount of MD/m2 if we double the concentration used compared to 10 litres/100m2.

4: flying insects, disinfection and backpack pumps

Again using a backpack sprayer and a dose of 10 litres/200m2 but this time setting the nozzle to a minimum, thus delivering a wide cone of spray at almost max pressure (more than 4 bars in any case), we can treat about 600m3 of ambient air, i.e. with a concentration per cubic metre of just over 16 ml/m3. Some 80% of this will settle on surfaces within a few minutes, while 20% will remain suspended in the air for a couple of hours (the smaller invisible droplets). This ensures good disinfection of both the horizontal surfaces and the ambient air (ambient air dose of about 3 ppm).

5: equipment and MDs

If we look at the example above, it appears that to be effective a dose of 3 ml/m3 must have a relatively high number of micro-droplets per cubic metre (obtained by adjusting the nozzle to a minimum and so increasing the pressure), but also by choosing the right MD. The information can be found on the label, the safety sheet and the technical data sheets authorised by the Ministry of Health. Other sources are specialist publications and the literature, provided these do not conflict with the official sources. We must never underestimate the value of a technical resource like hand-operated equipment: after all, if properly used, such equipment can disinfect 600m3 in less than 10 minutes (60m3/minute).

6: when great power comes into play

The above information for backpack pumps also applies to sprayers! The more powerful these are, the bigger the (potentially exponential) impact of even the slightest errors. If a sprayer is travelling at 8 km/h and covers an area 10m wide and 12m high, any error in the % used or, even worse, an inappropriate MD will affect 960,000m3 per hour. If a tree-lined avenue or park is being treated, an error could result in phytotoxicity. If there is a mistake in setting the supply pressure and/or flow-rate and/or particle size, there will be a good chance of uncalculated and “always” dangerous spray drift and/or environmental pollution and/or unwanted dripping and/or poor effectiveness. In other words: throwing money to the wind.

7: environmental constraints

Obvious, but often not considered as such: always make sure you have all the necessary permits before starting any job.

8: specific constraints

Equally important, you should check that the environmental conditions meet the required working conditions: no wind, signs indicating work in progress, no access to the public and the need to close all windows, no animals, no edible crops, safety hours and favourable weather forecasts.

9: equipment testing

The equipment must be checked to ensure proper operation (hoses, straps and nozzles first and foremost). In addition, all maintenance instructions must be read and complied with.

10: possibly the most important of all

Given that the above points are of a general nature and by no means exhaustive, I would stress that all procedures and instructions should be checked before starting. Moreover, it would be a good idea to keep a “common sense file”.


We reach our goals thanks to the equipment and products we use. Knowing every detail of their possible fields of application is increasingly necessary: consider all those nanotechnologies just around the corner.

Spazio Tre

P.le Archinto, 9
Tel. +39 02 69 00 12 55
Fax +39 02 69 00 12 77
P. IVA 08224100159
This email address is being protected from spambots. You need JavaScript enabled to view it.

Users Area

                • Forgot login?            • Register