How to remove black mould in student accommodation (and stop it coming back!)

Why black mould needs to be taken seriously: 

Every autumn, as the heating goes on and the windows stay shut, black mould starts to appear in student accommodation. Bathrooms, window reveals, the corners of ceilings and the backs of wardrobes are the usual places. For university estates and housekeeping teams, it can mean a steady stream of reports right through to spring.

Mould isn’t just unsightly. It damages decoration and furnishings, and the NHS advises that damp and mould can affect people’s health, particularly those with asthma or allergies. With damp and mould in sharper focus across the housing sector since Awaab’s Law came into force for social landlords in October 2025, students and parents expect it to be dealt with quickly and properly.

Why student rooms are so prone to mould

Student rooms tend to have a lot of moisture in a small space. Showers, cooking, drying laundry indoors and simply breathing all add water vapour to the air. In older college buildings with solid walls and single glazing, that moisture condenses on cold surfaces. Add rooms that are closed up during the day or empty over the vacation, and mould has everything it needs.

Why bleach isn’t the answer

Bleach-based sprays are often the first thing reached for, but they are mainly designed to whiten staining on tiles and other hard bathroom surfaces. Many aren’t suitable for painted walls, and they leave a strong chlorine smell in a room a student has to sleep in.

A better way: SANI-99™

SANI-99™ is a chlorine-free, fragrance-free disinfectant supplied as a powder in 6g sachets. For black mould, three sachets are dissolved in 1 litre of water. In independent testing to European standard EN 13697, SANI-99™ achieved a log 8 reduction of black mould and yeasts on surfaces.

It can be used on the walls, ceilings, window frames, bathrooms and kitchens where black mould takes hold, by trigger spray, low-pressure mister or fogger.

More than a maintenance issue

For those responsible for student welfare, black mould is more than a maintenance issue - it’s a duty of care. Leaving it untreated can expose students to avoidable health risks, damage trust in your accommodation and raise serious questions about whether the right steps are being taken to protect the people living there.

How to treat black mould, step by step

1. Find the cause. Check for leaks, condensation and poor ventilation. Mould will keep coming back until the moisture source is fixed.
2. Make up the solution. Add 1 litre of clean water to the spray bottle, then three 6g sachets of SANI-99™. Shake until dissolved.
3. Don’t brush or scrub first. Dry-brushing releases spores into the air. Lightly mist the affected area until it is wet.
4. Leave it to work. Allow 15–30 minutes contact time, then wipe away the dead mould and apply a light second spray.
5. Repeat if needed. Give heavy growth a second full treatment, then a light preventative spray every two weeks until the moisture problem is fixed.

Safety: 

Wear gloves at all times and eye protection when spraying. Add an FFP3 mask (or P3 respirator) for misting, fogging, heavy mould or confined spaces. Ventilate the room, keep students out during treatment, and never mix with bleach or other products. For professional use only.

Stopping mould coming back

• Ask students to open windows or use extractor fans after showering and cooking.
• Discourage drying clothes on radiators; provide drying space where possible.
• Keep a low, steady level of heating in rooms over the vacation.
• Report leaks, blocked gutters and failed extractor fans promptly.
• Follow up treated areas with a light preventative spray every two weeks until the cause is fixed.

Already used in Oxford

"Sani-99 is a great product for our scouts to use for our accommodation, we're more than happy with the results" - Michele Turner - Housekeeping Manager (Jesus College)  

Get started

SANI-99™ is available from Source as a Starter Pack, with a reusable 1 litre spray bottle and three sachets, and as a 25-sachet refill pack.  

Contact us on 01276 676006