Study question
The study asked two questions about the aerosols' physical characteristics. How did their volume-based spray particle-size distributions compare at release? How did instrument counts change over one hour in a controlled chamber for one representative product from each group?
Phase 1: spray particle-size distribution
ARE Labs used a Malvern Spraytec laser-diffraction system to measure each product at six inches from the detection laser. Each product was hand-actuated at least four times, and the measurements were averaged. D10, D50, and D90 are volume percentiles; D[4,3] is the volume-weighted mean diameter.
The table reports size on a volume basis. D50 marks the midpoint of the measured volume distribution; it is not a median based on particle count. D[4,3] and D50 describe different aspects of that same distribution, so their values can differ without indicating disagreement between instruments. They are not two independent measures of fragrance performance.2
The groups contained unequal numbers of products. A, B, and C each included three products; D included one. The displayed values are descriptive group averages, not inferential estimates of every product in a category.
Repeated hand actuations do not increase the number of independently sampled products. Averaging at least four actuations describes the measurement procedure for each product; group D still contains only one product. The three-product group averages and the one-product comparator therefore have different sample structures and do not provide equally broad estimates of a commercial category.
| Product group | PSD products | D[4,3] | D50 |
|---|---|---|---|
| Test Article A | 3 | 31.49 µm | 28.49 µm |
| Comparator B | 3 | 75.03 µm | 69.72 µm |
| Comparator C | 3 | 77.91 µm | 69.26 µm |
| Comparator D | 1 | 89.77 µm | 80.64 µm |
A, B, and C are averages of three products each; D is one product. Values retain the source report's displayed precision.
View figure data as a table
| group | D[4,3] | D50 |
|---|---|---|
| A | 31.49 µm | 28.49 µm |
| B | 75.03 µm | 69.72 µm |
| C | 77.91 µm | 69.26 µm |
| D | 89.77 µm | 80.64 µm |
- A, B, and C are group averages of three products; D represents one product.
- The chart is descriptive and does not show inferential uncertainty.
Under the reported measurement conditions, A had the lowest displayed group-average D[4,3] and D50 values. This is a result for the tested product set, not a universal ranking or evidence of sensory preference.
Phase 2: chamber count over time
One representative product from each group was dispersed into a sealed 16 m³ chamber. The report describes approximately 22 °C and 35% relative humidity, two mixing fans, and two chamber air changes per hour. A TSI Fast Mobility Particle Sizer model 3091 sampled at 30-second intervals during one-hour trials.
The study reports observations at 30-second intervals. Although the manufacturer lists a faster instrument time resolution, that capability does not establish that readings were retained or analyzed at the faster rate in this study. Interpretation should follow the reported study record.3
The FMPS measurement range was 5.6-560 nm. It measured electrical-mobility size and number concentration, but could not determine whether an individual measurement represented a particle or droplet or identify its chemical composition. The report also describes an aerodynamic particle sizer as a pretest instrument. Its role should be kept separate from the FMPS trial data and the optical Spraytec results.
The two phases used different measurement locations, size ranges, and distribution bases. A volume-based spray diameter measured near release cannot be substituted directly for a chamber number concentration in the FMPS range. The chamber counts do not track individual droplets measured by laser diffraction or describe material outside the selected instrument range. The phases address different questions, and their displayed values are not interchangeable endpoints.2,3
The chamber inputs were not equivalent. A3 was actuated for approximately 750 ms; B1, C2, and the single group D product were actuated for one second. The report does not provide emitted-mass normalization.
| Chamber product | Actuation | Starting count |
|---|---|---|
| A3 | Approximately 750 ms | 1.62E+05 particles/cm³ |
| B1 | 1 second | 4.46E+02 particles/cm³ |
| C2 | 1 second | 6.71E+03 particles/cm³ |
| D1 | 1 second | 2.93E+02 particles/cm³ |
The starting counts are not normalized to emitted mass or an equivalent delivered dose. Figure 12 in the source plots raw counts on a logarithmic scale.
The A3 count trace remained above the comparator traces throughout the reported hour. A3 also began substantially higher than the comparators, and its actuation duration differed. The report provides no normalized decay constants, half-lives, equivalent-dose comparisons, confidence intervals, or replicated chamber-trial statistics.
A higher trace throughout the hour does not, by itself, show a slower fractional decline. That comparison would need to account for initial concentration and relevant input differences. The starting-count table shows that the products entered the observation period at markedly different levels. The raw counts should therefore be reported separately from any normalized persistence claim, without assuming an unreported decay model.
Interpretation boundaries
The particle-size results support a specific comparison: A produced lower displayed volume-based size metrics than B-D in this tested sample set. The chamber results support a separate observation: the measured A3 count trace began higher and remained higher during the reported one-hour trial.
Neither result establishes how long people perceive a fragrance. Odor perception depends on chemical composition, vapor behavior, sensory thresholds, ventilation, deposition, use conditions, and other factors not measured here. Particle residence in this chamber does not establish odor longevity.
The study also does not establish inhalation exposure, lung deposition, toxicological safety, or clinical effect. The FMPS did not identify chemical composition, and the study did not measure breathing-zone exposure or biological response.
The historical report contains conflicting regulatory references in its GLP statements. It also contains multiple source dates, none of which has been established as a publication date. The report does not establish this study's accreditation or GLP status. ARE Labs' current laboratory accreditation is described in the related Quality Documentation page.
What the study contributes
Within these limits, the work shows how complementary aerosol methods answer different questions. A future claim-support program should define the intended claim first, normalize the relevant inputs, and predefine endpoints. Sensory, exposure, deposition, or safety methods should be added only when those outcomes are at issue.
Summary
For the client, the work distinguished volume-based particle sizing from one-hour chamber particle measurements. ARE Labs documented the tested product comparison and its limits: unequal inputs and starting counts prevent a normalized persistence claim. The findings provide a basis for planning a future claim-specific study; they do not establish odor longevity, safety, exposure, or clinical performance.