Chemisorption has been proved to be effective in removing many gas phase pollutants. There is a need to develop a simple and practical model to evaluate and to predict the performance of chemisorbent based air cleaners. In current study, two models with and without explicit consideration of intra-particle diffusion were developed and implemented for simulating chemisorption fixed bed. Chemical reaction is assumed to occur over sorbed phase contaminant. A standard test method was developed for performance evaluation, and to provide the model input parameters such as chemisorption capacity and reaction constant. The models are validated by comparison between the simulation and model-based test data of formaldehyde removal by chemisorbents. The pollutant transport and removal mechanism in the porous chemisorbent was analyzed through simulation. External mass transfer was found to have negligible effect comparing with internal mass transfer, and intra-pellet diffusion was the rate-limiting factor during the whole chemisorption process.