Indoor air quality and early detection of mould growth in residential buildings: a case study

Thank you very much for your very interesting work. Please see below some comments and suggestions that could help clarifying a few things in the present manuscript.

General remarks:

2.2 Monitoring campaign

Line 4-5 With the scope of identifying

Line 5-7 Can you please provide more information about the sampling procedure?

For the swab testing

1 ^st ) Can you please provide the rationale behind the selection of these particular locations (kitchen bench, hallway cupboard and bedroom) for wiping i.e. where they potential fungal reserves, where they dusty indicating potential storage of fungal particles etc?

2 ^ND ) what kind of swabs did you use i.e. premoistened or dry swab, solvent used etc.

3 ^rd ) was there a specific protocol followed i.e. wiping 10cm ² of the surface under examination

For the air sampling

1 ^st ) Can you please provide details about the sampling protocol followed i.e. sampling duration, airflow velocity if a pump or other mechanical mean was used, how many litres of air were sampled per room

2 ^nd ) Were the occupants allowed to carry out any activities prior to sampling i.e. vacuum, exercise, open the windows, etc? If not for how many hours were they not permitted to carry out any activities.

3 ^rd ) Can you please give some specifications of the air sampling cassettes?

For both swab and air sampling

1 ^st ) What methods were used for the analysis of the samples?

2 ^nd ) How do the surface and air sampling results complement each other?

3.1 Site Inspections

Could you please specify whether the fungal readings originate from?

2 ^nd Paragraph Line 6: I think there is a spelling mistake (raspatory or respiratory)

2 ^nd Paragraph Line 9-10: Could the elevated levels in the kitchen be associated to the fact that in kitchens the fungal readings might be capturing the existence of mould particles that originate from fruit, vegetables or food remnants that have infested by mould and have released spores or fungal particles over the previous days?

Figure 2: Could you please change the line for TVOCs so that the line becomes clearer in the figure?

Figure 3: Can you please delete the zero values for the 31/08 so that there are no vertical lines in the graph?

The CO2 levels seem to be lower than the threshold values you reported. The peak values might be a result of larger occupancy density and since it has not risen above the threshold levels at any time wouldn’t that mean that the property is sufficiently ventilated?

Thanks for the opportunity to read this interesting paper. It presents a thorough investigation of a home with severe mould and IEQ issues in Canberra, Australia. I think it is a useful contribution.

My major comment is that I think the authors need to be a bit more careful with their conclusions and generalising the results. For example, in the conclusions they state “Buildings with a high concentration of fungal spores are also more likely to present poor IAQ, high concentrations of particulate matter (PM10 and PM2.5), as well as a high level of CO2.” This was certainly the case in the studied building, but I am not sure you can generalise this to all buildings.

More minor comments:

Introduction

• I appreciate what you mean by occupant habits being a risk factor. But, something like having a cold home – and increasing the risk of damp – may not necessarily be a habit or choice, but a result of fuel poverty.

section 3.1

• were any mechanical ventilation systems present?
• raspatory should be respiratory

section 3.2

• Can you give more information on the air sampling? What equipment, what is FS, how was it counted? Did you follow any standard monitoring methods?
• in my experience, the kitchen can have higher levels of mould due to undetected leaks in the sink cabinet
• Figure 3 – I think it would be best to remove the measurements for 29/8-31/08. I initially interpreted it as CO2 dropping to zero, which is not the case.

Conclusions

I am not convinced that the evidence supports the conclusions. At least “Buildings with a high concentration of fungal spores are also more likely to present poor IAQ, high concentrations of particulate matter (PM10 and PM2.5), as well as a high level of CO2.” Yes, mould spores could be detected as PM, and CO2 is often used as a proxy for ventilation if there are indoor CO2 sources. But, with CO2 for example: there can be other causes of mould than just ventilation issues - for example damp and mould due to damage. So, I urge caution when in the conclusions, and would avoid generalising this based on the results of a case study investigation. Perhaps, though, the methods could be a easy low-threshold way of investigating possible problems prior to air sampling