It's only six more months until the millennium really starts. Odors are controlled through adsorption and chem-isorption methods. However, the big IAQ focus these days, and probably into the near future, is the control and remediation of molds and fungi. Some aspects of system maintenance, like coil cleaning, are being pointed to as solutions to rising health concerns.
More indoor spaces have some sort of air conditioning.
People are spending more time in these conditioned spaces. If the coil is also dirty, it serves as food for microbial growth. Again, the coil does not dry off. And clean the coil. There are design considerations that affect maintenance accessibility.