How should you read laboratory test reports for air purifiers?

Key points

• A lab report is only as useful as its test setup: chamber size, airflow, mixing, pollutant type, and sampling method.

• Check whether the report measured concentration in the room over time (what happens in the air) or only single-pass efficiency (what happens through a device).

• Pay attention to starting concentration, time to result, and detection limits. Results can mean different things depending on the baseline and instrument.

• Look for controls: a baseline decay curve, a “device off” condition, and repeatability.

• If the technology uses “active” chemistry (UV/PCO, ionisation, plasma), look for by-product checks (e.g., ozone, VOC intermediates), not only removal claims.

Laboratory test reports can be extremely informative, but they’re easy to misread. Two reports can both claim “high removal,” yet imply very different performance in a real room—because they used different chambers, different pollutants, different sampling, and different success criteria.

This guide is a checklist for reading test reports as a building owner, facilities manager, consultant, or technically curious buyer. The aim is to extract what they genuinely tell you—and what they don’t.

What kind of test report are you looking at?

Most air-cleaning reports fall into one (or more) of these types:

1) Chamber concentration decay tests

A pollutant is released into a sealed (or controlled) chamber, then the device runs, and the report tracks how the concentration changes over time.

What this is good for:

• Understanding time-to-clean in a bounded volume

• Comparing devices under the same method

• Seeing on/off behaviour

2) Single-pass efficiency tests

Air is drawn through the device, and the report measures pollutant levels upstream vs downstream.

What this is good for:

• Understanding removal efficiency through the device

• Comparing filter media under controlled conditions

3) “Real room” or field measurements

Not strictly “laboratory,” but often presented alongside lab work. These tests track PM/TVOC/CO₂ (and sometimes microbiological samples) in occupied spaces with the device on/off.

What this is good for:

• Seeing whether lab performance translates into day-to-day operation

• Understanding placement, mixing, and usage patterns

If your goal is “how quickly will my room improve,” chamber decay tests are often more interpretable than single-pass numbers—provided the chamber and sampling are well described.

Start with the test objective: what pollutant was used?

Indoor air is a mixture. Reports usually test a subset.

A useful first step is to map the test pollutant to your actual concern:

• Particles (PM₂.₅ / PM₁₀, smoke, dust, pollen)

• Gases/VOCs (formaldehyde, NO₂, SO₂, odours, representative VOCs)

• Bioaerosols (bacteria, fungi, viral surrogates)

If the test pollutant doesn’t resemble your problem, treat the result as limited.

(For a refresher on pollutant categories: Indoor air pollutants in modern buildings.)

Check the chamber size and mixing assumption

Why chamber volume matters

A device can look “fast” in a small chamber and “slow” in a large one. Always find:

• chamber volume (m³)

• fan speed/operating mode

• placement of the unit and sampling points

Mixing: Does the chamber behave like a well-mixed room?

Many reports implicitly assume the chamber is well mixed. In real rooms, airflow patterns create zones. A good report will describe:

• mixing fans (if used)

• sampling locations and whether they were averaged

• whether the device discharge created directional flows

If a report doesn’t mention mixing, interpret the decay curves cautiously.

Look at the time axis, not only the final percentage

A lot of reports emphasise a single headline like “99% removal.” That number is incomplete without time.

Ask:

• 99% in 5 minutes or 2 hours?

• does the curve flatten near a background level?

• does the device keep improving the air, or does it hit a limit?

For decision-making, “time-to-reach a threshold” is often more useful than “percentage removed after N minutes.”

Understand what “removal” means in the report

For particle reports

Particle results may be given as:

• mass concentration (µg/m³), or

• particle counts, or

• size distributions

Check whether the metric matches the claim (e.g., PM₂.₅ vs “smoke”).

For gas/VOC reports

Look for:

• the specific gas measured (formaldehyde vs “TVOC” are not interchangeable)

• the instrument type (sensors vs analytical chemistry)

• whether the report shows decay to stable end products or only disappearance of the target gas

For microbiological reports

Check:

• organism used (bacteria, fungi, virus surrogate)

• method (culture plates vs molecular detection)

• whether “inactivated” means “non-viable” (culture) or simply “not detected” (which can mean several things)

Pay attention to the starting concentration and detection limits

This is one of the most common misreads.

If a report starts at a very high concentration and ends at “below detection,” you need to know:

• what was the detection limit?

• how close was the final value to the background?

• was the instrument saturating at the start or near its noise floor at the end?

Statistics can be legitimate, but without detection limits and calibration information, you can’t judge how meaningful the final decimal places are.

Look for controls and baseline decay

A chamber pollutant can fall even without a device, because of:

• natural deposition on surfaces

• leakage or adsorption

• chemical reactions in the chamber

A good report will include:

• a baseline decay curve (device off)

• repeat runs/replicates

• environmental conditions (temperature and humidity)

If the device-on curve is only slightly faster than the baseline, the practical effect may be modest even if the headline percentage looks good.

If a report claims “disinfection,” look for dose and exposure conditions

For UV-based systems, effectiveness depends on UV dose (intensity × time) and airflow path geometry.

Even if a report doesn’t provide full photometric detail, it should describe:

• airflow rate

• residence time/chamber geometry

• whether microbes were aerosolised or placed on surfaces

The same logic applies to any inactivation claim: the mechanism needs exposure conditions that make sense.

If the technology is “active,” check whether by-products were measured

Some technologies create reactive chemistry as part of the cleaning mechanism (for example, UV/PCO, ionisation/plasma, ozone-based approaches). For these, a strong report not only shows removal of a target pollutant; it also checks for unwanted outputs.

Depending on the system, you might look for:

• ozone measurements

• NOx measurements (in some contexts)

• VOC intermediates (often aldehydes in oxidation processes)

This is where understanding secondary pollution is useful: remember to ask what might be created while “cleaning.”

Translate lab results into room decisions: CADR and eACH

If a report provides CADR (or enough data to infer it), you can estimate “equivalent clean air changes per hour”:

• eACH ≈ CADR ÷ room volume

That helps you compare lab performance to room size.

A short checklist you can reuse

When reading a lab report, check:

1. Pollutant: particles, gases/VOCs, or bioaerosols?

2. Method: chamber decay vs single-pass?

3. Chamber size and mixing: volume, airflow, sampling points?

4. Time-to-result: how fast does the curve drop?

5. Controls: baseline decay, repeats, conditions?

6. Detection limits: what does “not detected” actually mean?

7. By-products: were ozone/intermediates checked where relevant?

8. Relevance to your room: translate to CADR/eACH if possible.

Summary

Lab reports are valuable when you read them as engineering documents: define the pollutant, understand the test method, check controls and detection limits, and then translate results to room-relevant quantities. The best reports make it easy to see what the device removed, how quickly it did so, and whether the process introduced any unwanted by-products.