A 6 month old child attends with a 2 day history of runny nose and a cough. His mum reports he is maintaining his usual oral intake. On examination he looks comfortable at rest with no signs of chest recession. He is currently apyrexial, oxygen saturations are 96% and capillary refill time is less than 2 seconds. Fine crackles can be heard throughout his lung fields.
At what respiratory rate in this infant would you consider referral to hospital?