Urea injection is required in EU IV to EU VI applications as a mainstream technical direction. In heavy and some medium duty trucks, compressed air at 3-5 bar is available; therefore it can assist urea injection by mixing with urea liquid droplet and exhaust gases. The development of air assisted urea pump and injectors, seemly simpler than airless counterparts, poses multiple challenges. One challenge is to properly mix urea in the mixing chamber with the compressed air, leaving no residual deposits while achieving high mixing efficiency. Another is to maintain good spray quality for a given length of delivery pipe as the liquid phase and gas phase tends to coalesce as they propagate along the pipe flow direction. In addition, the urea pump and injector need to provide robust and reliable performance under stringent road conditions. Given these challenges, this paper addresses key development aspects for air assisted urea pump and injector with hope to provide insights on major design features.