Aniefiok E. Ite^{1, 2,}, Clement O. Ogunkunle³, Clement O. Obadimu¹, Ekpedeme R. Asuaiko⁴, Udo J. Ibok¹

Indoor air quality parameters were investigated in an occupied air–conditioned office and unoccupied air–conditioned office located in the Faculty of Natural and Applied Sciences Complex in Akwa Ibom State University – Nigeria, during the rainy (June – July) and dry (November – December) seasons of 2016. Particulate matter (PM₁, PM₂, PM₅, PM₁₀), temperature, relative humidity, carbon monoxide (CO) and carbon dioxide (CO₂) levels were simultaneously measured in fourteen (14) sampling days using Fluke 985 Particle Counter and Fluke 975 AirMeter. The concentrations of particulate matter in the occupied air–conditioned office during the rainy season ranged from 5152 – 5984 μg/m³ for PM₁; 2744 – 3015 μg/m³ for PM₂; 137 – 149 μg/m³ for PM₅ and 36 – 50 μg/m³ for PM₁₀ and in the unoccupied air–conditioned office, the concentrations of particulate matter ranged from 1898 – 2556 μg/m³ for PM₁; 987 – 1311 μg/m³ for PM₂; 38 – 59 μg/m³ for PM₅ and 15 – 24 μg/m³ for PM₁₀. During the dry season, the concentrations of particulate matter in the occupied air–conditioned office ranged from 5852 – 6510 μg/m³ for PM₁; 4490 – 4992 μg/m³ for PM₂; 335 – 362 μg/m³ for PM₅ and 59 – 69 μg/m³ for PM₁₀ and in the unoccupied air–conditioned office, the concentrations of particulate matter ranged from 2598 – 3112 μg/m³ for PM₁; 1168 – 1694 μg/m³ for PM₂; 153 – 257 μg/m³ for PM₅ and 29 – 42 μg/m³ for PM₁₀. This study has revealed that the particulate matter (PM₁, PM₂, PM₅, PM₁₀) concentrations in an occupied air–conditioned office were significantly (P < 0.001) higher than those obtained in unoccupied air–conditioned office during both rainy and dry seasons. However, the concentrations of PM₁₀ obtained in the present study were found to be much lower than the ambient maximum contaminant level for airborne PM₁₀ standard promulgated by the United States Environmental Protection Agency (USEPA) (150 μg/m³ daily average and 50 μg/m³ annual average) and World Health Organization (WHO) PM₁₀ guidelines values (50 μg/m³ daily average and 20 μg/m³ annual average). Although there were no significant relationships among PM₁, PM₂, PM₅, and PM₁₀ in occupied air-conditioned office, correlation analysis indicated that PM₁, PM₂ and PM₅ were significantly correlated at P < 0.01 in unoccupied air-conditioned office and correlation coefficients were different. Apart from suspended atmospheric dust and settling dust, human activities in the occupied air–conditioned office significantly influenced the particulate matter concentrations obtained compared to those obtained in unoccupied air–conditioned office in both rainy and dry seasons. Although the concentrations of CO and CO₂ were below detection limit (BDL), they indicated adequate air exchange at the time of the assessment in the air–conditioned office during the sampling period. The results obtained have revealed important contributions towards the understanding of particulate matter distribution patterns and provided baseline data that can be used for potential identification of human health risks associated with airborne particulate matter in air–conditioned offices in Akwa Ibom State University – Nigeria.

indoor air quality, particulate matter, air-conditioned office, staff exposure, Akwa Ibom State University