Far-UVC is ultraviolet (UV) light in the 200-230 nm spectral range. It has been called "An emerging tool for pandemic control" and is becoming increasingly popular as a promising technology for mitigating the transmission of respiratory infections. At current exposure limits, it looks to be safe for humans while being able to kill airborne viruses and bacteria. The currently most commonly used far-UVC lamps emit at 222 nm.

The American Conference of Governmental Industrial Hygienists (ACGIH) sets threshold limit values (TLVs) for ultraviolet exposure of workers. This is the de facto industry standard that other institutions adopt.

Given newly emerging evidence on the safety of far-UVC, ACGIH substantially revised their 8-hour exposure limits for far-UVC in 2022. The revisions were based on Sliney & Stuck 2021. The new guidelines set an 8-hour 222 nm UV-C exposure limit of 161 mJ/cm^2 for the eyes and 479 mJ/cm^2 for the skin. Before the revision, the 8-hour 222 nm limit was 23 mJ/cm^2 for both eyes and skin and hadn't been updated for decades.

A lot of new studies on the safety of far-UVC are currently underway. New evidence is expected to emerge in the coming years. Based on this, it is plausible that another upward revision of far-UVC exposure limits could happen.

This resolves YES if, before 1 January 2025, ACGIH releases a statement/document/announcement that specifies an upward revision of the TLVs in the 200-230 nm range.

It would also count as YES if only the skin or the eye TLVs were raised, but the other stayed the same. If e.g., the skin TLV is raised, but the eye TLV is lowered, I will make a judgment call if—all together—it seems like an upwards revision to me. For instance, a 50% increase of the skin TLV, with a 10% decrease of the eye TLV, would still be an overall upward revision for me.

If the TLVs are raised for some wavelengths in the 200-230 nm range but lowered for other wavelengths, I will resolve YES if, for >50% of the 200-230 nm range, the TLV is raised and the upward revision is larger than the downward revision of the rest of the range.