What's measured
A proper thorough examination does two different kinds of checking at once. It measures - airflow, velocity, pressure - and it observes - smoke, dust and condition. Neither on its own is enough; the value is in doing both together.
The short answer
A proper thorough examination does two different kinds of checking at once. It measures - airflow, velocity, pressure - and it observes - smoke, dust and condition. Neither on its own is enough; the value is in doing both together.
The detail
The quantitative side produces numbers. Airflow rates, capture and face velocities and static pressures are read with an anemometer and a manometer, and each is compared against the performance recorded at commissioning. These figures tell you, precisely, whether the system is still moving the amount of air it was designed to move and where any shortfall sits. Read alone, though, a good airflow figure is quietly reassuring in a way it has not always earned.
The qualitative side produces judgement. A smoke test shows where the air actually goes; a dust lamp reveals fine particles escaping a hood; and a visual inspection covers the condition of hoods, ducts, belts, bearings, fans, filters and general wear. This side tells you whether the air the numbers describe is genuinely catching the contaminant, or moving impressively while the plume drifts past the hood edge. A dust lamp is especially unforgiving here, because it shows the respirable fraction that no airflow figure can account for.
What it means for you
The two are deliberately complementary. A system can hit its airflow numbers and still fail a smoke test because a cross-draught is stealing the plume, and it can look clean to the eye while being measurably down on flow. A thorough examination that leaned on numbers alone, or on observation alone, would miss half of what matters and could pass a system that is not actually protecting anyone.
Judging performance means holding the measured values and the observed behaviour side by side and asking whether they agree. When the numbers are good and the smoke is drawn cleanly in, you have real evidence of control; when they disagree, that disagreement is the finding. This is why a competent examiner always does both, and why a report that quotes only airflow figures, with no observation behind them, is only half a test. The best examiners let the two argue with each other, treating a clean set of numbers and a failed smoke test not as a contradiction to be smoothed over but as the single most useful finding a test can produce.
The service behind the guide
We combine measured airflow, velocity and pressure with smoke, dust-lamp and visual checks, so your test judges the system on both, with a clear report and remedial actions.
Questions
Quantitative assessment measures numbers - airflow, capture and face velocities, static pressures - with instruments. Qualitative assessment observes behaviour and condition using smoke tests, a dust lamp and visual inspection.
Both. A competent examiner measures the airflow and pressures and observes the airflow and dust behaviour, then judges the system on the two together rather than on either alone.
Yes. A system can meet its airflow figures and still fail a smoke test because a cross-draught carries the plume past the hood, which is why observation is needed alongside the numbers.
Chiefly an anemometer for airflow and velocities and a manometer for static pressures, with each reading compared against the commissioning benchmark.
No. Numbers without observation are only half a test. A proper report shows both the measured values and the observed behaviour, and what was done where they disagreed.
Phoenix Duct Clean · by the numbers
We combine measured airflow, velocity and pressure with smoke, dust-lamp and visual checks, so your test judges the system on both, with a clear report.