What is the version of the following sentence with correct punctuation?

Air is contaminated with moulds and bacteria which thrive in damp and dirty places as well as with dust and other deposits which begin to collect in the ducting from the first day the ventilation is switched on And because people today often spend the majority of their time indoors the situation is made worse
Air is contaminated with moulds and bacteria which thrive in damp and dirty places, as well as with dust and other deposits which begin to collect in the ducting from the first day the ventilation is switched on. And, because people today often spend the majority of their time indoors, the situation is made worse.