Air staging strategy is a proven technology to provide efficient biomass combustion with less gaseous and particulate emissions. In this study, two different secondary air distribution modules are employed at two different axial positions from the bed surface in a 15 kW fixed-bed laboratory scale combustion system includes grate and underfeed bed stocker. The effects of air staging on temperature, burning rate, gaseous and particulate emissions have been assessed over a selected primary air flow rate and a range of secondary air flow rates. Secondary air inlet module with uniform distribution of air results in 50% CO reduction by shifting the combustion to a more fuel lean environment and high temperature in the post-combustion zone. Remarkable decrease in particulate matters smaller than 1 mu m is achievable through adjusting a uniform secondary air module in an appropriate distance from the bed. The non-uniform secondary air configuration increases the gaseous and particulate emissions than the uniform configu-ration. These results emphasise the need for further studies to better understand the effect of air staging on particulate and gaseous emissions. (C) 2016 Elsevier Ltd. All rights reserved.