> how long do the airborn droplets survive?
Not sure, but my understanding is that they fall to the ground and are less likely to be passed on due to inaccessibility as much as deterioration. (Might need to check that)
Most commonly dogs become infected if they
inhale the respiratory secretions of a dog infected with kennel cough - coughing, sneezing and watery discharges all shed replicated infectious disease particles into the environment and, consequently, the disease spreads and infects new hosts.
Dogs can also
ingest respiratory secretions contaminated with infective virus and bacterial particles. Such inadvertent consumption of infectious disease particles can occur if your pet eats or drinks out of (apparently clean) feeding dishes and water bowls that have been contaminated by a sick dog's respiratory secretions (e.g. nasal discharges).
> And can it be passed on from the owners clothing ?
It is possible for dogs to ingest infectious viral and bacterial particles when they lick the shoes, hands or clothes of a human that has been in hands-on contact with an infected animal. Dogs that sniff and lick hands and clothes can leave infectious secretions (e.g. snotty discharges) behind on those hands and clothes. They might even sneeze or cough on those hands and clothes, coating them with infectious aerosols.
If you have dogs living in close proximity to one another then you really ought to expect transfer - it would be be extremely difficult to isolate an infectious dog in a normal home. However you can apply good hygiene - such as that used when you or others have colds. Keep surfaces clean, wash bedding regularly, don't allow your dogs to eat or drink from each others bowls, wash door handles, wash hands regularly etc