The designation for Fire Safety purposes of common stairs etc in a house divided into 6 flat leases.

Other

Concerning Fire Safety
I am the freeholder of a house divided into 6 leasehold flats of which I own two. I run the freehold and services. I have recently been informed that I should upgrade the current number of fire extinguishers from the current 3 ( one for each floor) to 6 because of new BS standards.
However when I contacted the original free safety assessor he said it depended on the definition of what constituted "commercial" He sent....
"BS 5306-8:2012 Revision-Main points to consider. Changes made to the previous, 2000 version, of BS5306-8 will likely impact on premises that provide portable fire fighting equipment. Some points to note are;  Class ‘A’ Provision-Class A materials are generally present in all premises"
Apparently in this case 2 extinguishers are needed.
But what are class A materials and are they likely to be found in a norma flat?

I would like to add- would the stairways and internal common parts which are the designated fire escape route, be designated as either "residential" or "commercial"? It does not seem to me at all clear which. Not residential because not actually lived in..but why commercial as obviously not like office or shop property?.
So in summary could you advise, going on from this, what is reasonable in terms of number of extinguishers for such a commonly found property. Its over three floors with 2 one bed flat flats on ground and first and 2 studios in attic.