Noting the Differences: WOCDs Aren’t Night Latches, Vent Stops or Vent Limiters

By Kathy Krafka Harkema

The differences among some specialized types of window hardware and their designated functions can be confusing. Window opening control devices (WOCDs), for instance, are sometimes mistaken for hardware such as night latches, vent stops or vent limiters. These can look similar, but there are important distinctions.

ASTM F2090

WOCDs are devices that have been tested to the specifications within ASTM F2090, Standard Specification for Window Fall Prevention Devices with Emergency Escape (Egress) Release Mechanisms. ASTM F2090 is an important safety standard for window fall prevention devices that are releasable, allowing windows to be fully opened for emergency escape and rescue. The ASTM F2090-2021 ballot was recently approved, and the 2021 version includes new sections for manufacturers using supplier test reports. It also clarifies that partial compliance to the standard isn’t allowed.

Defining WOCDs

To meet ASTM F2090 requirements, WOCDs must limit the window sash opening to less than 4 inches—the dimension universally accepted in building codes for balcony railings or guardrail assembly openings. WOCDs must also be releasable by either two independent single-action devices, or one dual-action device. After the WOCD is released, it must allow the window sash to be fully opened, as needed, for emergency escape or rescue purposes. It’s also important to note that a WOCD must reset automatically when the sash is closed.

From an emergency escape and rescue opening (EERO) standpoint, there’s another important differentiator when it comes to WOCDs. The WOCD egress release mechanisms must be readily visible when the sash is in the fully closed position, or when the window sash has reached the controlled open position, or both. WOCDs require two separate, distinct, and consecutive actions to release them, as spelled out in ASTM F2090.

No matter what type, style, material or brand of window, operation of the sash must be independent of the disengagement of the WOCD. That’s a big part of what differentiates WOCDs from other types of hardware. It’s also important to understand that operation of the sash, including mechanical operators, cannot be considered as part of disengaging the WOCD.

Other Specialized Hardware

However, other types of hardware are often confused with WOCDs. Night latches or vent limiters simply limit the window sash opening to let air in or out for ventilation. They are not WOCDs. It’s important to recognize and understand the differences in their intended uses and purposes. Vent stops, vent limiters or night latches, which cannot be released and which restrict the window sash from being fully opened, should not be used on windows designated or intended for serving as EEROs.

FGIA will publish an updated technical document to explain the differences in specialized window hardware later this year.

Kathy Krafka Harkema is U.S. technical operations director for the Fenestration and Glazing Industry Alliance (FGIA).

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