Security air distribution devices are specialized grilles installed in secure facilities, such as behavioral health or correctional facilities, designed to reduce tie-off or ligature points that could lead to self-harm. Two risk-resistant face designs are used for security air distribution devices—passageway and perforated.

Perforated security grilles, which feature small circular openings stamped into the device’s face plate at regular intervals, are recommended for use in secure facilities by the leading standards organizations in the U.S. with some restrictions. It’s important to understand what those restrictions are to maintain compliance with these crucial safety standards.

What Are the Recommended Perforated Security Grille Hole Pattern Sizes?

The risk-resistance of a perforated grille pattern is correlated to its hole size. The smaller the individual holes, the harder it is to loop material through them. Over the years, standards organizations have lowered the recommended size for perforated holes to further restrict creation of ligature points. As of 2026, the recommended perforation hole sizes are as follows:

• 3/16” diameter hole patterns for the California Board of State and Community Corrections (BSCC), Behavioral Health Design Guide (BHDG) and National Institute of Corrections (NIC)

• 1/8” diameter hole patterns for the New York State Office of Mental Health (NYS-OMH)

Larger diameter hole pattern sizes that were once standard, such as 1/4” diameter or 5/16” diameter holes, are no longer recommended by any U.S. organization. Older facilities may have these sizes grandfathered in, while new construction and retrofit alike should adhere to the currently approved sizes.

What Areas of Secure Facilities Can Perforated Security Grilles Be Safely Installed?

Because perforated grilles cannot entirely eliminate ligature points, standards organizations’ recommendations for installation are limited to specific areas of secure facilities. These recommendations are not hard restrictions and are open to interpretation on a case-by-case basis.

Level 1/Low Risk/Patient Restricted Areas: Areas of a secure facility where facility inhabitants (patients for the purposes of this article) are not allowed under any circumstances, such as administrative areas or private offices. Because patients will never enter these areas, commercial grilles, registers, and diffusers are permitted for use.

Level 2/Medium Risk/Areas Under Regular Supervision: Areas of a secure facility where patients are regularly supervised and never left alone, such as activity rooms and counseling rooms. Perforated grilles are permitted to be installed in these areas by all standards organizations.

Level 3/High Risk/Areas With Minimal Supervision: Areas of a secure facility with minimal supervision where patients may be left alone for periods at a time, such as lounges, day-rooms, and hallways. California BSCC and BHDG allow perforated grilles to be installed here, while NYS-OMH does not recommend them.

Level 4/Maximum Risk/Unsupervised Areas: Areas of a secure facility where patients spend long periods of time alone, such as patient rooms and bathrooms. Perforated grilles are not recommended for use in these areas by NYS-OMH and BHDG. California BSCC allows the use of perforated grilles in maximum risk areas.

Approved Perforated Security Grille Hole Pattern Size and Recommended Risk Areas by Standards Organization

Why Do Facilities Choose Perforated Grilles?

Despite the extra considerations to using perforated grilles compared to passageway grilles, their benefits may lead secure facilities to install them in appropriate areas:

• Cost: Perforated grilles are less expensive than passageway grilles, saving secure facilities money.

• Weight: Perforated grilles are lighter than passageway grilles, which may make them more suited for lay-in ceiling applications.

• Airflow Restriction: Perforated grilles let air pass through more easily than passageway grilles, cutting down on the energy needed to move a similar amount of air.

Work with KEES to Understand Your Perforated Security Grille Options

Navigating the air distribution device recommendations from standards organizations can be daunting. KEES is here to help. We’ll work with you to perform a risk assessment and determine your relative energy usage requirements, guiding you towards the appropriate security air distribution device for your needs. Additionally, our top-of-the-line perforated security grilles come recommended by all major U.S. standards organizations, meaning you can’t go wrong with any KEES product.

Learn more about KEES Security Grates, Grilles, and Diffusers.