Bacteria in carpet

What is actually happening

Two things feed it. Oils — barefoot oils, the microbiology oils animals leave behind, food and drink worked into the pile — which are organic material sitting in a fibre matrix. And moisture that should not still be there: a carpet properly extracted is damp and dry in four to eight hours, while one left soaked keeps a wet pad underneath it for a day or more. Add a fragranced deodoriser applied at the end of a job with nothing to rinse it out and you have organic carrier, trapped moisture and body oils in one place. The room smells better for a week. Spiker makes no sanitising or health-outcome claims about any of this and measures none of it on a residential job.

How you prevent it

Subtractive rather than additive. Extract the oils out on a real cycle, get the recovery right so the pad is not left wet, and keep fragranced residue off the pile. Never set furniture back onto damp carpet — a sofa blocks airflow completely, and mildew under a piece nobody looks at is the most common callback in this trade.

Organic material plus moisture plus warmth is a growth medium, and a carpet supplies all three when it is left damp or loaded with body and animal oils. The point worth knowing is that a badly finished cleaning makes this worse rather than better, because residue is itself organic and it holds moisture.