"Black Toxic Mold" ?
This photo is an example of a serious mold infestation. The warm humid conditions near the hot water heater made for the perfect growing conditions for mold. A pin-hole leak in a copper water supply pipe provided just enough water to keep the gypsum board wall panels wet and allow the black mold to grow.
By the way, black is the most common color of mold. But, not all mold id black and not all black is toxic. However, in this case, testing confirmed that this was an example of Stachybotrys the well known "toxic" mold. Stachy as it is called in the mold remediation business can be harmful to humans because it produces very small spores that are able to get past the filtration abilities of the average person's respiratory system.
Our certified mold technicians were able to place the water heater room under negative air containment (to not spread the mold) while they removed the damaged wallboard and removed the microbial contamination, fixed the plumbing leak and prepared the room for new wall coverings. If you have a property with mold problems please talk to us. We're here to help with sensible solutions.