system
Given the following post, respond as if you're commenting on Reddit:
human
How are UV bulbs made "low ozone"?

I've purchased several fluorescent type UV bulbs that operate at 253 nm. A person may purchase two versions of the same bulb, regular and "low ozone" bulbs. If the bulbs are at the same frequency, how do the manufacturers decrease the ozone produced? Is there a standard for "low ozone"? or is it just what they feel like?

EDIT: Thank you for the replies. Yes, these are mercury bulbs.
gpt
Assuming it's a mercury lamp, it also emits at 185 nm.  This is causing most of your ozone. You need a fused quartz envelope to pass that deep of UV, so using regular glass will absorb it, reducing ozone production.