It is a popular scene in film and literature. The Victorian lady suddenly feels quite faint and needs to lie down. What was the reason for this? In part it’s due to the belief of the Victorian’s themselves that women were “the weaker sex” unable to deal with any kind of trauma. The authors and fledgling film makers of the silent movie generation wrote according to this view. It was a view that has persisted throughout the twentieth century. However, there may be a more substantial reason as to why it seems to have gotten into our common folk belief. It is because well to do Victorians who could afford it spent much of their lives under gaslight.
At the time, the leading company of fitters and suppliers of Gaslight were the Gas Light and Coke Company, but you didn’t need a Gas Meter box like those from https://www.meterbox.co.uk/gas-meter-boxes just yet. They produced two types of Gas for gaslights, natural and Coal.
The pipes that sent the gas into the home were not always sound. They could be of cheap manufacture. Therefore there was considerable leakage of gas into the home reducing the oxygen. The well to do Victorian lady did not go out very much. So, after breathing this in all day, it’s no surprise that they may have felt a little unwell for most of the time.