Hi. Do not worry. The sinuses can not actually drain directly into the chest , so there is no chance of pneumonia development unless you have not treatment. If you are suspecting a sinus problem I would advise you to consult an ENT Surgeon. Clinical check-up, ENT Endoscopy and CT Scan of the sinuses is the only modality to get a proper diagnosis whether you have sinusitis or not and if present what type? *Whether this is infective in origin- you need a long course of antibiotics, decongestant tablets and nasal drops, steam inhalations, anti-inflammatory medicines.. * If allergic n origin- you just need an antihistamine and if required steroids in oral or topical forms. * If Fungal or so, you need a Surgery. * If there are associated problems like deviated nasal septum or so- you may need corrective surgery too. So this i very important to consider these points for a correct diagnosis if you want a cure. Do not be worried about pneumonia.