I recently ran a small field test in a set of primary school classrooms to answer a practical question facility managers ask all the time: are electrostatic sprayers measurably better than manual fogging when judged by simple microbiology pass/fail criteria? I designed a pragmatic, low-cost microbiology protocol that any cleaning team or facilities manager can use to compare two disinfection methods and get reliable, actionable results without a fully-equipped lab. Below I share the approach I used, the results patterns you can expect, and practical tips for running your own comparison.
Why this question matters
Classrooms are high-touch, high-occupancy spaces where infection control and perception of cleanliness both matter. Suppliers often make strong claims for electrostatic sprayers (e.g., Victory Innovations, Clorox Total 360) or fogging machines (thermal or cold foggers like Magnum or SurePure), but those claims aren’t always tested under consistent field conditions. I wanted a simple, reproducible way to determine whether one method delivered a practical microbiological advantage — not lab-perfect elimination of every organism, but whether surfaces met a sensible pass/fail threshold after treatment.
Overview of the testing approach
My goal was to keep testing simple and affordable while giving clear yes/no answers. The approach uses settle/contact sampling and aerobic colony counts with a pass/fail threshold based on colony forming units (CFU) per sample. You can do this with a basic field microbiology kit (agar contact plates, incubator, and a simple colony counter or visual estimate) or send samples to a local lab if you prefer.
Key elements of the protocol I used:
Sampling plan (simple, repeatable)
Here’s the plan I followed across four classrooms — you can scale up or down depending on resources.
Pass/fail criteria I recommend
For a straightforward verdict I used the following:
| Metric | Threshold | Pass = |
|---|---|---|
| Contact plate (25cm²) | ≤50 CFU/plate | Acceptable microbiological load |
| ATP reading (optional) | ≤250 RLU (depends on device) | Low organic residue |
| Visual residue/odour | None/neutral | Pass for user acceptability |
I favour the CFU threshold because it measures viable bacteria, which is most relevant to infection risk. ATP is useful as a rapid adjunct but picks up non-microbial organic matter too and thresholds vary by device.
Results patterns I typically see
Across multiple tests I ran in different schools, three clear patterns emerged:
Practical pros and cons
When interpreting pass/fail results, context matters. Here’s a compact comparison I use when advising clients.
| Factor | Electrostatic Sprayer | Manual Fogging |
|---|---|---|
| Coverage uniformity | High — wraps around surfaces | Variable — depends on operator and nozzle pattern |
| Speed | Fast for medium-sized rooms | Fast but can require masking/ventilation |
| Operator skill | Moderate — training reduces errors | Higher — technique critical for good results |
| Consumables/cost | Higher capital cost; moderate fluid use | Lower capital cost; fluid use varies |
| Residual wetness/odour | Typically less dripping | May leave more wet residue if over-applied |
Safety, dwell time and product compatibility
Two important operational notes:
How to run your own A/B test in one day
Here’s a compact checklist I give to clients wanting a one-day comparison:
Interpreting the data
If both methods produce passes at the chosen threshold, choose based on cost, speed, sustainability, and staff acceptance. If one method yields more passes or fewer outliers (failed high-CFU spots), that’s a strong indicator it will deliver more reliable day-to-day results.
Finally, remember this is about operational improvement, not perfection. I encourage teams to combine microbiological checks with visual audits and staff feedback to pick the solution that fits their budgets and routines.
