# Development of an Automatic Low-Cost Air Quality Control System: A Radon Application
As much as this technique is an effective, low-cost, easy-to-implement solution for gas dilution, which works simply by exchanging indoor and outdoor air, it implies certain aspects that can compromise energy efficiency in ventilated spaces [15]. This could result negatively in other aspects, besides working against energy efficiency: it could considerably worsen the comfort of those present in a heavily ventilated area (including noise pollution, inadequate temperature ranges, unpleasant air currents), all of which would eventually result in additional costs, both personal and economic [16]. Radon measurement protocols should therefore ensure quality and consistency in radon levels while minimizing any possible negative side-effects that solutions such as continuous ventilation would cause, resulting in a sustainable, cost-effective control of indoors radon. Describing the most appropriate indicators allows us to measure the involved variables in the current processes and to measure the effect of taken actions, and therefore develop qualitative and quantitative descriptors that can be used for comparing and evaluating the taken actions [17]. Air quality is a key factor in environmental indicators, and its importance has grown during the recent decades since it has been linked to both climate change and human health [18; 19]. Within air quality indicators, pollution is defined as \"the contamination of the physical and biological components of the earth/atmosphere system to such an extent that normal environmental processes are adversely affected\", and it may lead to chronic diseases [20]. Even though gas pollution and air quality might be some of the most relevant and more studied factors within pollution, noise and light [21; 22] pollution have also been proved to be related to population well-being, and therefore should be taken into account when implementing ventilation strategies. Energy consumption and efficiency are two closely related concepts. Vast quantities of energy are consumed as economy [23] and people's expectations of comfort grow [24], which makes it vital to move towards more self-sufficient, renewable-based, pollutant-mitigating consumption policies [25]. Buildings constitute one of the main consumers of energy in cities, besides industry and transportation systems. They must be constructed to be safe, efficient, and self-sufficient, according to their geographical situation [26] and use. A considerable number of certifications are available nowadays to ensure the accomplishment of these aspects [27]. These issues are also contemplated in the concept of Indoor Environmental Quality (IEQ), which popularity has grown as the general public became increasingly aware of the health hazards related to contaminated air. IEQ involves several factors, as it refers to the quality of the interior spaces of a building in relation to the well-being of those that make use out of it. It includes previously mentioned aspects such as air quality, comfortable temperature, noise pollution, all of those aspects related to this study. Research has shown that IEQ has a relevant impact on the performance of those who occupy the space [28; 29; 30]. Besides the before-mentioned health, economic and environmental impacts, poor IEQ in buildings makes its occupants less happy and less productive, specifically in workplaces [31]. Most existing buildings suffer from inadequate performance, including energy consumption and overall comfort (noise, air quality, temperature, air currents, etc. ), which inevitably results in an undesirably low level of IEQ. [32]. In this work, we designed and developed a system that can autonomously control the air quality of the residence where it is deployed. The automatic air quality control system is based on a previous work of some of the authors of the current work [33]. In that work, the authors developed a secure radon monitoring system that could send alerts to the selected users based on the radon levels it measured.