Each character in a module with a gas cloud suffers the effect of the gas as indicated on page 97. For some toxins there may be a passive check involved.

Roll a die at the end of each phase after checking for gas effects. The gas dissipates on a 1 or 2.

If an external door was opened at any point during the phase or the module is a functioning Life Support module, make a second dissipation check.

If a character is holding an external door open, make an additional dissipation check.