Nonwovens are materials that are permeable and are manufactured using methods different from the traditional methods of fabric manufacture. Nonwovens are characterised by high porosityand randomly laid fibres. They are also of low strength and there is need to impart strength to the fabrics by needle punching, thermal bonding and chemical bonding. During this thermal bonding or chemical bonding the fabricsmay undergo structural changes and this may result in pore size and characteristics changing. In this research Nonwoven sampleswere made by carding polyester, polyvinyl alcohol and polypropylene fibres, to form a web of fibres before needle punching after which the fabrics underwent thermal bonding at temperatures of 150 RÂC and 160 RÂC. The time at which the samples were exposed to thermal energy (dwell time) was varied between 1 minute and 6 minutes. To analyse the effects of heat and time, air permeability and average pore size diagrams were used. Results showed a decrease in the air permeability with time as well as a decrease in the pore, after thermal bonding. Results also showed that the fabrics with the higher density generally had lower air permeability than thosewith lower density before and after thermal bonding.