Ventilation, indoor air quality and thermal comfort in India’s leather footwear manufacturing cluster: a tier-resolved field study

Abstract Footwear manufacturing in India is carried out in establishments of very different size, from formal factories to single rooms in converted houses, yet the air these workers breathe for nine to ten hours a day has not been compared across them. Air temperature, mean radiant temperature, relative humidity, air velocity, CO2, total volatile organic compounds (TVOC), formaldehyde and particulate matter measurements were taken at the breathing zone in three of the enterprise tiers of the Agra cluster, with each measurement coinciding with a simultaneous ASHRAE 55 ballot. The campaign resulted in 378 valid worker-session records in four seasons and 147 days. Ambient air standards from India, WHO guideline values and occupational exposure limits were used to compare concentrations. All of the pollutants increased in a linear fashion from large to cottage scale, and air velocity decreased from 0.80 to 0.16 m s − 1 and accounted for 79% of the variance in pollutant levels between the tiers. With CO2 fixed, the air velocity was also independently and negatively associated with TVOC and apparent formaldehyde, indicating that the gradient is driven by dilution and not by occupancy. 91.3% of sessions had apparent formaldehyde levels above the ACGIH TLV and all sessions in the two smaller tiers were also above the ACGIH TLV; no session anywhere was below the WHO PM2.5 guideline. Air movement was not related to outside temperature, but dropped considerably when adhesive was being applied, thus emission and dilution were inversely related at that time. The organising variable is enterprise size for occupational exposure in this sector, through the means of ventilation.