UV systems were used at that time to kill airborne bacteria in particular!

The increasing availability of antibiotics and new preserving materials, cleansing and disinfecting agents to improve hygiene then however caused a reduction of the preventative technology.

In many areas the modern room air conditioning seemed a comfortable and hygienic solution to dealing with airborne organisms. It was only from the mid 70ies that certain limitations were understood and since then ongoing researches did show the backside of the medal (Sick Building Syndrome, Building Related Illness).