The manuscript entitle “Quantifying Functional Group Compositions of Household Fuel Burning Emissions” describes the application of FTIR analysis for the identification of organic functional group (OFG) in particulate matter emitted during combustion of different fuels by household appliances. In addition, different combustion phases are investigated. The results obtained by FTIR analysis are compared to those obtained from traditional analytical techniques, including thermal-optical analysis (for total OC determination) and GC-MS (for the quantification of PAHs).

The manuscript presents new data on OFG composition of primary emissions and describes the value of FTIR measurements to investigate the aromatic aerosol component, which is extremely relevant for defining the impact of combustion aerosols on human health. Some more discussion would be useful to understand the discrepancies between thermal optical OC and FTIR OC.

The manuscript is clear and well written. I recommend its publication after minor revision.

Specific comments.

Section 2.1 Can the authors add any details about the dilution ratio of the sampled emissions and the temperature at sampling point?

Line 78 What is the ratio between the OC quartz back filter and the  OC measured on the Qf collected in parallel?

Line 198: As suggested by the authors, one of the reason for the underestimation of FTIR-OC compared to TOT-OC is the "operationally defined EC-OC separation". Do the authors observed a link between the OC underestimation and the pyrolitic carbon quantified by thermal-optical analysis?

In addition, is it possible that the sensitivity of FTIR is reduced by the signal attenuation due to high EC loading? The agreement between TOC-OC and FTIR-OC is generally higher in ambient samples, where I assume the OC to EC ratio is higher. Do you see a link between the underestimation of FTIR OC and the OC to EC ratio?

Line 209-202: Can the authors comment on the potential artefact of soot/graphitic carbon/EC  on the aromatic CH signal? (Fig. S12) The conclusion about the contribution of multiple PAH, in addition to those quantified by GC-MS is convincing. Nevertheless, one of the strongest points of the manuscript is the ability of FTIR measurements to describe the totality of the aromatic component. So it would be good if the authors could say something about the potential artefacts on the PAH quantification due to EC.

Technical corrections

Several citations are reported without leaving a space before the brackets. For ex. lines 13 and 15.

Line 194: S12 should be S13

Line 197: I guess the term "variability" would be more accurate than "uncertainty"

Line 208 : S11 should be S12

Fig S11 and fig 7 looks the same. Please remove one of them

The manuscript titled "Quantifying Functional Group Compositions of Household Fuel Burning Emissions" by Li et al. discusses the utilization of Fourier transform infrared spectroscopy (FTIR) to analyze fine particulate emissions originating from various cookstoves. The study presents source profiles of functional groups derived from different fuel types and cookstoves. Quantitative outcomes were achieved by comparing the results with OC/EC and GC-MS measurements. Overall, the manuscript is well-written and aligns with the scope of AMT. I recommend its publication after some minor revisions.

Minor aspects

1. The authors need to clearly state how the baseline is determined. Which is to say whether the baseline is defined by individual Teflon filters before sampling, or a unified baseline is used. It would be important for the researchers who would like to follow this method.

2. It would greatly benefit readers to include an example plot in the supplementary information illustrating the subtraction process of both blank baseline and EC-influenced baseline.

3. Line 149, it would be valuable to provide insights into the factors contributing to the substantial variability observed in charcoal combustion tests. Possible connections with temperature or other combustion conditions could be explored and explained.

4. Line 196, it's reasonable to assume that the volatilization of organic compounds might lead to lower concentrations on PTFE filters, contrasting the adsorption of VOCs on quartz filters. While a 40% underprediction compared to TOT OC is acceptable, the authors should provide more comprehensive reasoning behind this discrepancy.

5. Line 229-240, consistently elevated OM/OC ratios (1.6-1.8) were observed in the cookstove test utilizing the FTIR method, a value that appears to surpass the OM/OC ratio derived from the AMS method (ranging from 1.3 to 1.5 for primary emissions, as reported by (Canagaratna et al., 2015)). It is advisable for the authors to discuss further on this aspect, providing in-depth discussions and explanations concerning this disparity.

6. I recommend including a table summarizing the functional group abundances alongside their corresponding typical wavenumbers from source profiles of different cookstoves. This addition will be immensely helpful for future researchers interested in employing the same method.

Reference

Canagaratna, M. R., Jimenez, J. L., Kroll, J. H., Chen, Q., Kessler, S. H., Massoli, P., Hildebrandt Ruiz, L., Fortner, E., Williams, L. R., Wilson, K. R., Surratt, J. D., Donahue, N. M., Jayne, J. T., and Worsnop, D. R.: Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications, Atmospheric Chemistry and Physics, 15, 253-272, 10.5194/acp-15-253-2015, 2015.