Why window between the bathroom and kitchen in the Khrushchev?

Do not get tired of repeating that today most of the country lives yesterday afternoon. No, it's not about nostalgia and the memories of the Soviet Union. It's about our housing stock: 60-65 per cent of the population lives in houses built during the Soviet era, and understand all the subtleties of Soviet engineering apartment and not all succeeded.

Now you know what purpose is actually doing a small window between the kitchen and bathroom?

I - do not know until today.

In search of an answer to the question reached the Internet and saw a bunch of conflicting options. Especially liked the two.

1) In the USSR required to install window between the rooms, so that when domestic gas detonation shock wave "found out" through the window, rather than reflected back from the wall.

This version looks absolutely ridiculous: a window in curbing such power is clearly not an assistant.

2) The sunlight had to penetrate two windows, one big kitchen and a small "Bathing" and hit photons bacteria that accumulate bathroom in moist air.

This version is no longer, if you look at the height of the window: the direct rays of the sun at such an angle to simply not covered.

Finally, the true version.

Admittedly, the second version of the Internet has been closer to the truth. In fact the window between the kitchen and the bathroom made for additional lighting bathroom. It turns out, according to Soviet standards insolation (room lighting) the sun for at least two hours a day was to get through this window and cover the bathroom.

Profit - saving electricity for lighting bathroom light bulb Ilyich.

In fact the box has been ineffective, and new homes they have not put in mind of their uselessness.