What is the requirement for ozone-generating devices in ventilation systems?

• A. They can emit up to 50 ppb.
• B. There is no standard for ozone emissions.
• C. They must comply with UL 2998 for zero ozone emissions, with a maximum of 5 ppb ozone emission.
• D. Ozone devices are prohibited entirely.

Answer: (C)

Ozone-generating devices in ventilation systems must be tightly controlled to protect indoor air quality. The requirement is that any ozone-producing device be certified to UL 2998, which verifies zero ozone emissions, with a practical limit of no more than 5 ppb in the air under normal operation. This certification ensures the device truly minimizes ozone release rather than merely claiming low levels. The 5 ppb cap accounts for measurement uncertainty while keeping ozone levels far below typical outdoor concentrations and well within IAQ safety boundaries. So, the correct practice is to use UL 2998 certification for zero-emission claims, with a maximum of 5 ppb ozone emission.