This heater is from the turn of the 20th century, about 1903. Like many bath heaters, it has interlocking controls to prevent the heater from running unless water was flowing through it to cool it.

These people thought gas fumes were of no importance, so not only did they not provide for venting; they made venting impossible, by placing a fancy chrome piece on top of the heater that prevented people from adding their own.

Such ideas are now extinct.