harry wrote:

The whole world and the air everywhere is full of spores and
bacteria. Why get your knickers in a twist? Mould in your ductwork
can be killed by fumigation. However when the job is done, it will
simply re- establsh it'self unless the cause is rectified. This may
involve preventing condensation by insulating the ductwork or changing
temperatures or airflows. Our biological defences have evolved over
millions of years to defendus agianst all these things or we would all
be dead by now.

Ah, but legislation to protect the evolutionary defectives from being
exposed (i.e., peanuts, any asthma-inducing substance, etc.) is slightly
skewing the population into the vulnerable hallway.