"Janet Baraclough" wrote
The message
from "JennyC" contains these words:

i always thought that carbon monoxide was poisinous to humans too?
Or are the concentrations so low as not to matter?

The machines emit carbon dioxide, CO2..the same as you do when you
breathe out.

CO2 ( in expelled breath) is what attracts midges to people and
animals.

Aha, there's your answer then. Never mind the technology, just learn
better breath-holding techniques, David Blaine style.

--
Sue