MHRV (Mech Heat Recovery Ventilation) cleaning filters help!

Scuff

Hi, not sure if this is in the right place but I'll try anyway - we live in a relatively new flat that has a HRV unit installed. I know enough that I know the filters need cleaning / changing, but although we were supplied with a 'maintenance' booklet (I use the word maintenance lightly as it is the most un-useful booklet I have ever seen!) and all that says is to 'remove filters, wash, dry and replace in unit'

Can anyone help me with this - how do I wash them / what with, mild detergent, hand wash? (this is a guess) They are well in need of cleaning, but the individual 'units' in each room are blowing air out rather than what I would think they would do (suck air in??) I'm presuming this is purely because the filters are gammed up - is this most likely the case?

Apologies if these are stupid questions, and thanks in advance!!

Scuff

The air that comes out of the units is cold, just to clarify it's not doing any actual heat recovery!!