How Do You Predict the Level of Respiratory Irritation?

There's a four tiared irritation level that goes all the way from nun to i. And basically it's the amount of coughing and sneezing heard within 30 seconds. Life guards just sort of have an idea of what it feels like, so in some sense, it could be a subjective day to set. The first model we looked at that seemed more intuitive is a wind based model.