Cleaning Air Conditioner Coils

[Guest guest]

I have taken to heart the posts regarding the necessity to clean a/c

coils--I believe it was said each season. So, I've tried to learn a

bit about the process and have a few questions.

Here goes:

When should this be done?

Should it be done for central a/c?

Is it safe to use a chemical cleaner called Acti-Klean (used by my

HVAC co.) which is rinsed off with water after application?

Any help will be greatly appreciated. I have become extremely

sensitive to everything inhaled & ingested so each decision has become

a " project. "