Histopathology labs use formaldehyde.

The limit for airborne exposure to formaldehyde set by OSHA the Formaldehyde Standard (TWA) is 0.75 ppm in an 8-hour time-weighted average (officially 1 ppm) and 2 ppm for a 15-minute Short-Term Exposure Limit (OSHA STEL). By the way, in 1987 TWA was 3 ppm.

The hospital wanted that these requirements should be met in order to make it safe for the lab technicians.

This was achieved by two strategies: 1. Use dilution ventilation with adequate makeup fresh air 2. Use air pattern to ensure that the formaldehyde does not dissipate all over the lab. This was achieved by using ceiling mounted non aspirating diffusers & exhaust air being picked at low level using return air risers.