UL 325 is the Underwriters Laboratories standard for safety covering door, gate, louver, and window operators. For automatic gates, it defines operator classes for residential, commercial, industrial, and restricted access sites, identifies the entrapment zones around a moving gate, and spells out the protection required to keep people from being caught or injured. Operators are tested against the standard by recognized laboratories such as UL, ETL, and MET, and a listed operator carries that laboratory's mark on its label.
Entrapment Protection Types
UL 325 recognizes several methods of protecting the areas around a moving gate. Most compliant systems combine two or more of these:
- Type A, inherent entrapment protection: built into the operator, it senses an obstruction and reverses the gate.
- Type B1, non-contact sensors: photo eyes that detect something in the gate's path.
- Type B2, contact sensors: safety edges mounted on the gate or posts that react on contact.
- Type C, inherent force limiting: an adjustable clutch or similar limit on how much force the gate can apply.
- Type D, constant pressure control: the gate moves only while a person holds the button.
What UL 325 Requires Today
The current standard is the seventh edition, in effect since 2018. Under it, a compliant gate operator will not run until its required safety devices are installed, connected, and recognized by the control board. The safety device is no longer an accessory you can choose to skip. It is a prerequisite for the gate to move. Here is what that means in practice.
- Two independent means of entrapment protection per direction: each direction of travel that has an entrapment zone requires two separate protections. Because the operator's built-in obstruction sensing counts as only one of them, every compliant installation includes at least one external device, and most include several.
- Monitored external devices: photo eyes and safety edges have to be monitored, meaning they communicate with the operator continuously so the control board can confirm they are present and working. If a device is missing or faulted, the operator stops operating rather than running blind.
- Approved devices only: because the operator and its safety devices are tested together as a complete system - generic sensors and field workarounds such as faking a device with a resistor are specifically prohibited.
- Manual release: the gate must be able to be disengaged and opened by hand during a power failure or emergency.
- Warning signage: clearly visible warning signs must be posted at the gate.
The number of required devices depends on the gate category. A horizontal slide gate requires two Type B sensors while swing gates require a single Type B sensor.
Why Older Gate Operators Behave Differently
If your gate does not behave the way the requirements above describe, you are not alone, and your operator is probably not broken. The current rules arrived through two major revisions, which left three distinct generations of operators in service today. They can look nearly identical on the outside but behave very differently when it comes to safety devices.
- Before 2016: external safety devices were recommended, not enforced. Many of these operators were installed with no photo eyes or edges at all, relying on inherent reversing alone (Type A).
- 2016: these operators accept monitor devices but are not required for the operator to function.
- 2018 to date: operators will not operate without the required monitored devices. This is the current standard described above.
There is no regulation forcing you to retrofit a working pre-2016 gate, but adding photo eyes and safety edges to an older operator is one of the most worthwhile safety upgrades you can make. If you want to pin down exactly which generation you own, our full guide walks through it step by step: how to tell which generation your gate operator is.
Still Have Questions?
Not sure what your operator requires to run and comply, or which devices pair with it? Our team can confirm what works with the exact model you own or are considering.
Talk to an expert at (800) 555-6017, Monday through Friday, 8AM to 4PM PST.