Monitoring indoor air quality is becoming crucial as people spend most of their time indoors. In recent years, respiratory problems such as chronic obstructive pulmonary disease and asthma appear as among the common diseases that are the reasons for hospitalization among people. Monitoring the indoor pollutant, using the low-cost sensor-based IoT system, can play an important role in the management of these chronic conditions. In this paper, we set out the design of a trial involving an unobtrusive IoT-based monitoring system to observe indoor environment passively in the house of people suffering from Asthma. The system monitors Particulate Matter (PM2.5 & PM10) and Carbon dioxide (CO2) in the indoor environment together with householder's indoor activities such as type of cooking, smoking, ventilation hour, cleaning, and so on.