Divertor effects on the particle confinement time in a tokamak plasma are investigated by modelling of particle, momentum and energy transports in the divertor plasma and particle transport in the main plasma, with a simplified model for neutral-particle transport. The divertor plasma has three equilibrium states in a limited range of the ion flux entering the divertor. It is found that the existence of the three equilibrium states might lead to mode conversion of the particle confinement characteristics during additional heating.