the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Sep 2026
A Chamber-Based Experimental Framework for Comprehensive Mechanistic Studies of Ageing-Driven Changes in Biomass-Burning Aerosol Properties
Abstract. Biomass burning (BB) aerosol particles can significantly impact climate, air quality, and human health. While studies have advanced our understanding of the impact-related properties of the particles, detailed investigations of both driving factors and mechanisms under controlled conditions of dark aging or photooxidation remain limited, especially across fuel types and burn phases. Here, we describe a BB aerosol facility at the University of Manchester that couples an Esse 175F commercial wood-burning stove, housed in a mobile unit outside the main laboratory and supplied with ambient combustion air, to the 18 m³ Manchester Aerosol Chamber. The facility enables batch-mode experiments under controlled dilution, temperature, relative humidity, oxidant exposure, target initial particle mass loading, and dark or illuminated aging conditions. Its batch configuration uses moderate, rather than high, continuous dilution, thereby limiting rapid dilution-induced perturbations while maintaining stable conditions and particle concentrations suitable for filter-based analyses, long-term parallel continuous measurements, and slow-response instruments that are difficult to deploy in short-residence-time flow systems. Measurements include particle size distribution, chemical composition, black carbon, volatility, hygroscopic growth, cloud condensation nuclei activity, optical properties, ice-nucleating ability, and gases. This facility, therefore, provides a repeatable, flexible system and platform for mechanistic and multiparameter investigation of fresh and aged BB aerosol. Experiments conducted in April and September 2022 demonstrated those capabilities across fuel types and combustion phases. They also characterized the facility, showing low background PM levels (<1 µg/m³), with primary gases and PM concentrations typically stabilizing within no more than 10–30 min after smoke injection.
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Status: open (until 17 Nov 2026)
- RC1: 'Comment on egusphere-2026-4932', Anonymous Referee #1, 15 Oct 2026 reply
Data sets
DataSet for "A Chamber-Based Experimental Framework for Comprehensive Mechanistic Studies of Ageing-Driven Changes in Biomass-Burning Aerosol Properties" Sara Aisyah Syafira https://doi.org/10.5281/zenodo.22108209
Model code and software
DataSet for "A Chamber-Based Experimental Framework for Comprehensive Mechanistic Studies of Ageing-Driven Changes in Biomass-Burning Aerosol Properties" Sara Aisyah Syafira https://doi.org/10.5281/zenodo.22108209
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- 1
This paper describes a new facility to generate smoke consistently for chamber experiments. The design concept is novel and interesting to readers of Atmospheric Measurement Techniques. Several initial experiments are described to show the versatility of the facility for mechanistic studies of smoke particle aging processes. The focus of the experiments are properties of the smoke particles, using fast measurements of size distributions, chemical composition, and optical properties, plus a few gas phase species, slower time-scale measurements using filters and offline analyses, and short time-selected sampling periods for understanding hygroscopic growth and cloud condensation nucleation activity. The recommendations below should be made to the manuscript to make it more acceptable for publication.
1) It is inherently difficult to describe the creation of a new facility without revealing any scientific results that have not yet been published unless that is the intent. Here, there were specific examples (Figures 6 and 8) that are presented that were analyzed further for a paper under review (Syafira et al., 2025). Rather than preempting the results of that paper, other examples of experiments that were already published (Chen et al., 2025; Evans et al., 2024 and 2025; Oghama et al., 2025 and 2026; plus others) could be presented or at least summarized in the facility manuscript. This would be an expansion of section 3.2.4 and minimizing what is described related to Figures 6 and 8. Especially important is further highlighting the longer time-scale results of the previously published work such as the filter and offline analyses mentioned in section 2.4, which strengthen the argument that this type of facility is needed. Summaries of the results of these papers in a later section (not just citing them in the methods section) would be very useful. As with any reproductions of potentially copyrighted figures, if included, usage should be authorized or the figure sufficiently altered.
2) A main focus of creating this facility is to obtain reproducibility in the experiment and several repeated experiments were described in Section 3.1.4, with some variability between them. Parts of Tables 2 and 3 which presented the consistency were difficult to interpret. Are all of the units “ug per cubic meter”, resulting in unitless ratios? Also, the ratios of “Org” and “BC” relative to “PM” were fairly small and did not sum to one (except for the smouldering-softwood experiments) as expected if all of the units were the same. What else is contributing to “PM” besides “Org” and “BC”? The relatively inert tracer of carbon monoxide (CO) is commonly used as the denominator in many studies examining biomass-burning aerosols. Why wasn’t it used here? The standard deviations of the gas phase ratios (O3/PM, NOx/PM, NO/NO2, and CO/PM) are frequently as large as their mean values. This weakens the argument that the initial conditions were sufficiently repeatable. While the smouldering experiments could potentially be difficult to capture repeatable, initial conditions, it’s expected that there is significantly less variability in the flaming initial conditions. This was not obvious from the way “repeatability” was presented.
3) Related to the above is the stability of the smoke during “dark” or “non-photoaging” experiments. These experiments are presumably meant to understand how stable the smoke particles are over the course of holding the smoke in the chamber for several hours. Because “photoaging” and “non-photoaging” experiments were presented together, it was unclear if the smoke really was stable in the chamber over long periods of time or if it changed due to coagulation, settling, loss to the walls, etc. It would be helpful to have a separate section describing just the results of the stability of the smoke for these conditions.
Minor comments:
1) The overall presentation was sloppy and the manuscript needs careful reading for accuracy and consistency. Figure numbers do not match with the text, especially in the SI. There are typos, such as figure captions with the figures transposed (Figure 7), the caption for Figure S12 with incorrect colors and panel labeling, line 449 “… that absorption of the total absorption …”, the fuel type sources in parentheses are not included in the caption for Table S1, "Evan et al." in line 460 should be "Evans et al.", plus many other typos. The naming/labeling/codes of each experiment is inconsistent throughout the paper (for example, “Flaming-Photoaging 7 April 2022” in Figure 6, “F-SW-1” in Figure 8 and “SF-P-1” in Figure S2 are probably the same experiment). The text in some figures is illegible (e.g., Figure S1). Each experiment stage (injection, mixing, and stabilization, in addition to “lights on”) should be more clearly marked on each figure, since “time after lights ON” and “time after experiment started” do not mean the same thing. Time is presented inconsistently as hh:mm:ss or X.XX hours. Sentences sometimes are too long and confusing (for example, line 299-301).
2) Define acronyms, especially in the introduction (note that FLAME is an experiment/study performed at the Missoula Fire Science Laboratory facility), and maintain consistency throughout the rest of the manuscript. It was confusing that both an SMPS and DMPS were mentioned (e.g., Figure 2 shows results from an SMPS and Figure S1 shows results from a DMPS), yet they do not appear to refer to the same instrument according to Figure 1.
3) The taxonomy “Category VIIa” mentioned in line 77 is meaningless without looking up the citation and needs more context.
4) Some details were incomplete or missing. For example, the modified ejector-dilution system is critically important for delivering the smoke particles to the chamber. Yet, there was no information in the manuscript about how this system works or how it was modified. Cleaning and mixing procedures were also minimally described and insufficient for understanding the workings of the chamber without delving into the original literature describing the chamber. For example, what does it mean that the chamber is “1/3 full” prior to smoke injection (line 146)? What is involved in “harsh cleaning” (line 148)?
5) The last paragraph of section 3.2.4 seems to be a summary of the paper (rather than supporting the section) and could be omitted.
6) Section 4 mentions measuring CO for understanding dilution effects. The CO from the compressed air system should also be monitored. Suggest also measuring the greenhouse gases in the same places as CO.
7) The last paragraph of section 4 mentions ambient air conditions. These should be checked for each experiment and added to a simplified version of Table S1 (such as omitting the column for the experiment name).