Air quality is the overall description of air pollution levels in a defined area that may affect the environment and public health. Over the years, increasing levels of air pollutants from natural and human-related sources lead to poor air quality. In urban areas where there are higher concentrations of people and air pollutants, poorer air quality would mean posing more detrimental health risks for its residents. Most exposed would be transport workers such as traffic enforcers, drivers and daily commuters. Previous studies have proved that air pollutants coming from different components of train cabin and ventilation system are significant sources of harmful air contaminants that could cause health risks and safety risks to passengers. Health effects of air pollution range from acute symptoms such as coughing and respiratory infections, to development of chronic diseases and even mortality. This paper summarizes significant findings on air quality inside the MRT 3 train cabins, including air contaminants and its effect to health risk of passengers. The air contaminants assessed include carbon dioxide (CO2) and atmospheric particulate matter (PM2.5 and PM10). Also, a survey was conducted to determine the common illnesses experienced by the passengers and its causes. The results of the study revealed that concentration levels of CO2 have strong positive correlation (r=0.828) to the volume of passengers inside the train cabin while presence of particulate matter such as PM2.5 and PM10 has weak negative correlation (-.0.055 and -0.210) to the volume of passengers. However, concentration of air pollutants must still be reduced since some passenger reported common illness such headache, dizziness, sickness, and breathing difficulties when riding MRT trains. Hence, the study recommends some interventions to maintain good indoor air quality of the train cabins like installing small-scale air capture technology to lessen the CO2 concentration and installation of air vent to lessen the atmospheric particulate matter inside the train cabins.