What's measured
Airflow is invisible, which makes it easy to assume a hood is catching what it should. Smoke testing removes the assumption. By releasing a visible tracer at the point that matters, it lets you watch the air do its job - or watch it fail to.
The short answer
Airflow is invisible, which makes it easy to assume a hood is catching what it should. Smoke testing removes the assumption. By releasing a visible tracer at the point that matters, it lets you watch the air do its job - or watch it fail to.
The detail
A smoke tube or smoke generator releases a controlled puff of visible smoke at and around the hood, the release point and the operator's position. The smoke follows the air, so it shows directly whether the airflow reaches out to the source and draws it in, or whether it drifts, stalls or heads somewhere else entirely. Where a plume is pulled crisply into the hood, the capture zone is doing its work; where it hangs, curls back or slides past the edge, it is not.
That simple picture reveals faults that numbers alone can hide. Smoke exposes dead spots where air barely moves, cross-draughts from doors, fans or open windows that push contaminant off course, reverse flow, and leaks where a system draws air in through gaps it should not. It also maps the real extent of the capture zone, showing how far from the hood the pull is still strong enough to matter.
What it means for you
Like the dust lamp, smoke testing is qualitative - it does not produce a reading - but it is immediate and persuasive. An operator who sees a smoke plume ignore the hood and drift into their own breathing zone understands the problem far better than they would from an airflow figure on a report. It turns an abstract capture velocity into something visible at the exact spot the contaminant is released. That visibility is often what finally persuades a workforce to position the hood properly and keep it there, which matters more to real exposure than any figure on a certificate.
Its place is alongside the measured tests, not instead of them. Airflow and static pressure readings quantify what the system is doing; smoke shows where that air actually goes; a dust lamp shows what the contaminant does. In a thorough examination the three are used together, so a system is judged not just on the numbers it produces but on whether the air visibly reaches the source and carries the contaminant away.
The service behind the guide
We use smoke visualisation with airflow and static-pressure measurement to show whether your hoods truly capture at source, with a clear report and remedial actions.
Questions
It is the release of a visible tracer smoke at and around a hood so you can watch the airflow. The smoke follows the air, showing whether the contaminant would be drawn into the hood or drift away.
It shows the direction and reach of the airflow - dead spots, cross-draughts, reverse flow, leaks and the true extent of the capture zone - things that airflow numbers alone can hide.
No, it is qualitative. It does not give a reading, but it shows immediately and visibly whether air is being captured at the source, which is often more convincing than a figure.
A smoke plume will visibly bend away from a hood when a door, fan or open window is pushing air across the capture zone, revealing a draught that could be carrying contaminant into the breathing zone.
No. It works alongside airflow and static-pressure measurement and dust-lamp observation. The numbers quantify performance, smoke shows where the air goes, and together they give a complete picture.
Phoenix Duct Clean · by the numbers
We use smoke visualisation with airflow and static-pressure measurement to show whether your hoods truly capture at source, with a clear report and remedial actions.