Everyone working in offices, shops, factories, hospitals, schools, laboratories, etc. requires a minimum standard of fresh air to produce a healthy working environment. One way that this can be provided is by effective general ventilation.
Dust and debris found in unclean ductwork, together with temperature and humidity levels, have been linked to the growth and spread of MRSA and other microorganisms in hospitals. It is similar to how flu and other common cold infections spread through poorly maintained and unclean workplace systems. These systems must be kept clean and maintained on a regular basis.