Mould can seriously affect human health. The quantity of mould, type of mould present and individual susceptibility are all factors related to the level or degree of health risk. Mould-test kits are available that determine the presence of mould and identify what type of mould is present. You can make a mould test kit yourself using a few simple items.
Place the Petri dish on a flat surface. Put clear tape inside the dish, with the sticky side up. Place enough tape to span across the dish. The tape will catch any airborne mould spores. Mould releases spores as a way of migrating. When the spores come into contact with water or moisture, they are able to form new mould colonies.
Place a second Petri dish in the air duct above the return air vent. Make sure the inside is lined with tape just like the previous step. Any mould spores travelling inside the ventilation systems will pass over the dish and cling to the tape.
Perform an analysis. After allowing the Petri dishes to sit overnight, place them under a microscope. If you know what mould looks like, you can identify its presence in the air. Dust particles are likely to show up in the Petri dish also, so be certain not to confuse the two. If you cannot or prefer not to do a technical analysis, there are companies you can send collected air samples to. They will perform the analysis and provide information on mould presence and type.
Perform a visual inspection. Many mould test kits will ask you to take a sample of the suspected surface mould with a swap. This is so the mould can be identified for any toxic types like Stachybotrys and Aspergillus-Niger. It also will determine if the sample is a mould or a mildew, which are often confused since both moulds and mildew prefer warm and moist environments like bathrooms. Moulds, however, are typically black, green, red or blue in colour. They can also appear fuzzy or slimy depending on the type. Mildew is usually grey or white and can be powdery or downy. A simple visual inspection should indicate whether the surface fungi is a mould or mildew.
Follow the HPA recommendation on testing. The degree and type of mould growth and individual susceptibility make it impossible to determine acceptable levels. This is why the Health Protection Agency (HPA) state that sampling and culturing are not reliable methods of determining health risk. Testing may be subjective and the HPA recommends any mould discovered should be removed immediately to minimise health risk.
Having a laboratory perform a mould test for you can be quite expensive.