Black or Soty Mould In The Home - Clean Cleaner

What Is That Black Mould

What is Black Mould (or more often called Sooty mould) and where does it come from?  Mould is a term used to describe fungi which colonise areas in thread-like structures called hyphae. Moulds are eukaryotic cells, meaning they more closely resemble plant and animal cells than they do bacteria - however, they are still microorganisms.

Like all living things, mould needs water, food, and oxygen to survive, and it’ll be no surprise to you that your home is perfectly suited to providing all three essentials. A typical colony of mould will feast on dead organic material, and are extremely important in aiding the decay of matter and freeing up nutrients - the cycle of life!

The dead organic material includes wood-based products (including gypsum board drywall), and some species can even degrade synthetic adhesives and paint. Dust that lays on surfaces within your home can be enough substrate to yield fungal growth, thus metal, ceramic, and plastic are also open to being habitats. As we’ve already discussed in a previous blog post, dust is virtually impossible to eradicate, and with dust comes dust mites, which mould consume the fecal matter of.

Is mould harmful?

Mould spores are everywhere in our environment. Being microscopic, it means that they are often light enough to travel via air currents, and they are capable of surviving in conditions that are not beneficial to more mature fungal organisms. This ability to lay dormant means that mould will often start to grow between 24-48 hours once favourable conditions are achieved.

There is no definitive answer to what constitutes low and high levels of exposure to mould, and thanks to our old friend evolution, our bodies are proficient in preventing harm come to us from background exposure levels.

Some people either have, or are susceptible to developing asthma and exposure to mould can aggravate the condition as well as more general allergies. Additionally, people who have a weakened immune system are more at risk, including people with HIV, cancer or those whom are on immunosuppresants.

Mould release mycotoxins that can be harmful to other living things, including humans. Some fungal species secrete multiple mycotoxins and some mycotoxins are secreted by multiple species of fungi. Exposure normally comes from ingestion of mycotoxins, however, inhalation and absorption through the skin is not uncommon.


Now, as your home is almost certainly composed of wood, metal, plastic, and/or glass, and unless you live in a completely sterile environment you most likely live surrounded by dust and thus mould. Humans, as well as mould, need oxygen too. So that leaves water (humidity or water patches) as the variable that can be altered in our favour to prevent the excessive growth of mould.

Condensation occurs when moist warm air comes into contact with a cool surface, and water droplets form on said surface. Condensation is a large contributing factor to an increase in abundance of water, but one that can usually be remedied. Firstly, and most simply, try to reduce the amount of condensation that you produce. This can be done by putting the lids on pans when cooking, or drying clothes outside.

If you dry clothes on the radiator, remember to let the humid air out and the fresh, cooler air in by opening the windows slightly. Extractor fans in both the bathroom and the kitchen will remove moist air out of the room to the outside, and are usually very cost efficient.

Because the warmer the home is, the less of a problem condensation is, if you home suffers from inadequate insulation then this could be an area that may well be worth investing in. For instance, loft insulation should be to a depth of 270mm. Additional measures include insulating any cavity walls, draft-proofing exterior doors, and making sure windows are at least double glazing.

Heating all rooms of your home, including the lesser used ones will reduce condensation build-up because there will be fewer cold spots for water droplets to attach themselves to.


First of all, let’s do things properly and get out some proper personal protective equipment (PPE). Even if the contaminated area is small, who wants to disturb fungal spores and either inhale, ingest, or dermally absorb them (or a combination of the three)?

Wear a long-sleeved jumper and trousers (bonus points if it’s a jumpsuit), along shoes, socks, and gloves so that as much skin is covered as possible. Some goggles as well as a filter mask to prevent anything getting in the eyes or lungs.

Hard surfaces should be cleaned with a mixture of water and washing up liquid. Dig out your brush from the back of the cupboard and start scrubbing. Don’t be afraid of putting your elbow into it (figuratively not literally)!

You can mix one part chlorine bleach with 10 parts water and apply this if the surface the mould is residing on isn’t made from natural material, i.e not wood or plant-based. We’ve written a blog post that details why bleach shouldn’t be used on wood that you can read here. Remember to be careful when handling bleach and not to mix it with anything that contains ammonia or an acid as this will cause the release of chlorine gas (deadly). Keep it out of reach of children and pets too.

For furnishings or content that is not a hard, inorganic material there are special mould remediation companies that should be able to help you. Remember though that it is often the case that the remediation costs more than the contaminated contents are worth.

Even mould that is dead can cause harm to humans, and the goal isn’t necessarily to kill it but to remove it from an area with as little cross-contamination as possible.

Thanks for reading this blog post, it's very kind of you. If you enjoyed it, please give it a like or share it with someone you think would appreciate it too! We've written about some other interesting topics as well, including why bleach is a terrible cleaner, and the fascinating world of dust - both are well worth a read!