Agree with mold mildew, as many of these species can be powerful allergens. CDC data supports this, although CDC remedies which include the use of Sodium Hypochlorite only stun/kill molds/mildews but do not remove the cells which can be the nutrient source for successive species. Biologists (mycologists) would recommend the use of 'caustics' to dissolve the cells. The danger of cleaning fungals is the spreading/release of spores; such cleaning should be done 'wet' to prevent spreading of the spores ... and aspiration of the spores into your lungs.
Strong caustic detergents such as Sodium Silicate based (Tuff-e'Nuff or Roll-on) or TSP or lye-based cleaners used in animal husbandry, etc. should be considered - Not to be used on painted or varnished surfaces.
Once thorough cleaning/rinsing (never clean mold/mildew when its dry, always 'wet-down') is accomplished ... consider to spray-on commercial 'mildew block' (3M) or simply spray on caustic detergents and simply let dry - such would be the modern equivalent of 'white-washing'.
Upholstery foam can be a potent a reservoir of fungal spores, so consider to replace with mold/mildew resistant foam .... or 'treat' the foam with toxic gases that kill/stun the fungals.
Paraformaldehyde (as a gas) can be used to treat 'foam'; the Para-F crystals will release into a gas when exposed to atmosphere. Put the foam into a large plastic bag, apply paraformaldehyde crystals (wrapped in cotton gauze to contain crystals) into the bag with the foam and apply vacuum to 'squeeze down' the foam then quickly seal ... the Para-F will out-gas into the tightly sealed bag ... Keep sealed for several days. After several day and in the open, open the bag to remove the Para-F, then pump the bag and its contents to reduce the Para-F concentration a few times (changes the air/gas inside the foam structure). Para-F is a potentially dangerous to human lung tissue gas, .... wont be available in 'green/eco' states where 'chemicals' usage by consumers is prohibited.
ALL black molds and mildews should be considered to be toxic to human respiratory systems - the worst is 'stochybatris autra' which is quite common in wet basements, etc. CDC has specific recommendation for the safe removal of 'stochy' - mostly 'kill in place', then rip-out and replace.
Check out the CDC website or your local health department sites for 'the details'.