How long does a person need to consider themselves contagious after having walking pneumonia?

Pneumonia. For bacterial pneumonia, you are no longer contagious after taking an antibiotic for 24 hours. Viral pneumonias are contagious until cough disappears. Chemical and aspiration pneumonias are not contagious.
Not contgious. Most pneumonias do not spread from person to person like head colds, there develop when bacteria living in the nose and mouth are aspirated into the lungs. There are exceptions if you have viral pneumonia or pneumonia from the flu. In those cases you could transmit it for a variable period of time until you are no longer sneezing or coughing.