As per my own experience gas geyser are not safe.once my neighbour fainted in the bathroom recently, I rushed him to a nearby hospital had no clue of what caused it.
“Her cousin told me he had collapsed in the bathroom, which was poorly ventilated. Any delay in medical care would have been fatal, ” said doctor who treated him
And one of my friend told he usually feels giddy and breathless after a bath. “Although his bathroom is adequately ventilated, sometimes it is suffocating, ” he said.