For the air exhaust plus smoke evacuation system, the problem of secondary smoke evacuation arises when smoke spreads to adjacent smoke-control zones.

Though the authors note as a curiosity that campaigns against secondary smoke predated the evidence that it did any harm, they show no desire to explore this seemingly reversed causality.

This battery cannot be used in combination with other types of primary or secondary batteries, or the abnormal charge or discharge will make batteries overheat, smoke, deform or burn.