INCHEM-Py v1.2: a community box model for indoor air chemistry

Abstract

Abstract. The Indoor CHEMical model in Python, INCHEM-Py, is an open-source and accessible box model for the simulation of the indoor atmosphere and is a refactor (rewrite of source code) and significant development of the INdoor Detailed Chemical Model (INDCM). INCHEM-Py creates and solves a system of coupled ordinary differential equations that include gas-phase chemistry, surface deposition, indoor–outdoor air change, indoor photolysis processes and gas-to-particle partitioning for three common terpenes. It is optimised for ease of installation and simple modification for inexperienced users, while also providing unfettered access to customise the physical and chemical processes for more advanced users. A detailed user manual is included with the model and updated with each version release. In this paper, INCHEM-Py v1.2 is introduced, and the modelled processes are described in detail, with benchmarking between simulated data and published experimental results presented, alongside discussion of the parameters and assumptions used. It is shown that INCHEM-Py achieves excellent agreement with measurements from an experimental campaign which investigate the effects of different surfaces on the concentrations of different indoor air pollutants. In addition, INCHEM-Py shows closer agreement to experimental data than INDCM. This is due to the increased functionality of INCHEM-Py to model additional processes, such as deposition-induced surface emissions. A comparative analysis with a similar zero-dimensional model, AtChem2, verifies the solution of the gas-phase chemistry. Published community use cases of INCHEM-Py are also presented to show the variety of applications for which this model is valuable to further our understanding of indoor air chemistry.

Indoor cooking and cleaning as a source of outdoor air pollution in urban environments

“…This paper uses the indoor air chemistry model, INCHEM-Py (INdoor CHEMical model in Python). 59,60 This model has been recently used to provide insight into oxidant surface chemistry, VOC emissions from plastic, and domestic cooking activities indoors. 29,61,62 INCHEM-Py is a zero-dimensional chemical box model which provides predicted concentrations of indoor gas-phase species over time, assuming a single well-mixed spatial environment.…”

“…INCHEM-Py calculates indoor photolysis rates by adding the contribution from attenuated sunlight through windows, to that from indoor artificial lighting. 60,73 Gas-to-particle partitioning is present in INCHEM-Py, 74,75 but only for α-pinene, β-pinene and limonene.…”

“…A new development to INCHEM-Py (v1.2 (ref. 60)) is the addition of primary emissions from common indoor materials. Wood and paint are commonly found in homes, and are known to emit indoor air pollutants, primarily short and long-chained aldehydes.…”

“…Surface-specific oxidant deposition initiated emissions are also present in the model for ozone and hydrogen peroxide, as outlined in Carter et al (2023) 61 and Shaw et al (2023). 60 The model does not consider resuspension from surfaces.…”

“…The chemical loss rate for the near-field species as they move outdoors is calculated off-line, based on the rate coefficients in the MCM 64 and assuming realistic outdoor concentrations of the oxidants. 60 For loss via photolysis once the species pass outdoors, the outdoor photolysis rates are calculated in INCHEM-Py, but without applying an attenuation factor as we would to calculate indoor photolysis rates. Note that we are only interested in the near-field concentration changes, not the impact on outdoor air pollutant concentrations.…”