1. Occupational asthma with latency: this asthma type is when the signs and symptoms of asthma occur after a period of time ("latency") after being exposed to the environmental irritants. e.g.: John starts working at a factory where chemicals are used the first week of January. At the end of March he starts developing the signs and symptoms of asthma. The period of time from when he started the job in January to when the signs and symptoms of asthma started in March is the "latency period".