Problems lay in the areas you can’t reach; the indoor coil, fan and drain pan and line are all moist environments which mould, fungus and bacteria thrive in. This is where that bad smell comes from!
The best way to ensure that your home is protected is to have the mould, fungus and bacteria removed from your heat pump, then have preventative treatments applied that will protect your system against recontamination.
A contaminated heat pump with unacceptable levels of mould & bacteria can suppress your immune system, cause cold & flu-like symptoms, skin irritations, hay fever & trigger asthma attacks.
If you want to provide your family with comfort controlled air that is also healthy then there is a solution… have your unit professionally cleaned and sanitised.