In the world of commercial building design and fire protection, few questions cause as much debate as smoke management in vertical shafts. If you are an architect, engineer, or building owner, you have likely asked: **Are smoke curtains required at elevators?**
The short answer is: **Not always, but they are one of the five approved methods to comply with the International Building Code (IBC) for hoistway smoke protection.** While traditional fire-rated elevator doors are excellent at stopping flames, they are notoriously poor at stopping the spread of smoke. Because elevator shafts act as chimneys during a fire (a phenomenon known as the "stack effect"), smoke can travel uninhibited to upper floors, causing loss of life and property damage.
With the updates in the **2024 IBC**, smoke curtains have become a more prominent and code-approved solution. This article explores exactly when and why you might need an elevator smoke curtain, the code requirements, and how they compare to alternatives like enclosed lobbies and pressurization systems.
## The Problem: Why Elevator Shafts Are "Smoke Funnels"
To understand the requirement for smoke curtains, one must first understand the danger of an unprotected hoistway. During a fire, hot gases and smoke seek the path of least resistance. An elevator shaft provides a perfect vertical pathway, allowing smoke to travel rapidly from the fire floor to all other floors in a building .
Standard elevator doors are tested for fire resistance (to contain flames), but they are not typically designed to meet stringent air leakage requirements. Gaps between the doors and the hoistway walls—often necessary for the door to operate—allow toxic air to pass through . This is why building codes have evolved to require "smoke and draft control" at these openings.
## IBC Code Requirements: The Five Approved Methods
The requirement for protecting elevator hoistways is primarily found in **Section 3006 of the International Building Code** (specifically 3006.3). If an elevator hoistway is not required to be enclosed in a shaft (or if the building design requires protection), the code mandates that openings into the hoistway must be protected to prevent the movement of smoke.
Historically, the most common solution was the construction of an **enclosed elevator lobby**. However, lobbies take up valuable real estate and disrupt architectural flow. To address this, the IBC provides alternatives.
According to the **2024 IBC Section 3006.3** and recent code proposals (like G165-25), protection of elevator hoistway doors can be achieved by any of the following five methods :
1. **Enclosed Lobby with Fire Partitions:** A standard lobby separating the hoistway doors from the floor area.
2. **Enclosed Lobby with Smoke Partitions:** Similar to above, but with smoke partitions rather than full fire partitions.
3. **Additional Doors (Swinging or Sliding):** Smokeproof doors installed at the hoistway opening.
4. **Elevator Hoistway Pressurization:** A mechanical smoke control system that uses air pressure to keep smoke out of the shaft (per IBC 909.21).
5. **Smoke-Protective Curtain Assembly:** A deployable smoke curtain installed at each elevator hoistway door opening.
Therefore, smoke curtains are not just a product; they are a **code-recognized alternative** to traditional lobbies .
## What is an Elevator Smoke Curtain?
An elevator smoke curtain is a passive fire protection system. It consists of a fire-resistant fabric rolled up inside a header box, usually installed discreetly above the elevator door frame on each floor .
When a building fire alarm system is activated—or specifically when smoke is detected in the elevator lobby or machine room—the curtain deploys. It descends vertically across the elevator opening, sealing the gap between the hoistway door and the wall. This creates a barrier that contains smoke to the floor of origin, preventing it from migrating through the shaft to upper levels .
### How They Work:
- **Detection:** The system is triggered by the fire alarm system or a dedicated smoke detector.
- **Deployment:** The curtain drops via gravity (fail-safe) at a controlled speed to prevent injury.
- **Sealing:** Technologies like "GuideLock" ensure the curtain seals tightly against guides, containing smoke.
- **Operation:** Most systems include emergency break-glass switches or buttons on either side, allowing first responders or trapped occupants to open the curtain temporarily .
- **Reset:** Once the alarm is cleared, the curtain automatically retracts.
## Testing and Standards: UL 1784 is the Key
For a smoke curtain to be accepted as a compliant alternative to a lobby, it must pass rigorous testing. The magic number to look for is **UL 1784**.
Section 3006.3 requires that smoke curtains comply with "the smoke and draft control requirements in Section 716.2.2.1.1 when tested in accordance with **UL 1784** without an artificial bottom seal" .
- **UL 1784** is the standard for "Air Leakage Tests of Door Assemblies." It measures how much smoke can pass through or around the assembly.
- The test is conducted **without an artificial bottom seal**, meaning the curtain cannot rely on a fixed physical seal at the floor to pass; the design of the fabric and guides must do the work .
- Additionally, the control unit for the curtain must be listed to **UL 864** (Standard for Control Units and Accessories for Fire Alarm Systems) .
## When Are Smoke Curtains the Best Option?
While any of the five methods can technically satisfy the code, smoke curtains are often the preferred solution in specific scenarios.
### 1. When Space is at a Premium
In Class A office buildings or high-end hotels, every square foot of leasable space matters. Building an enclosed elevator lobby consumes floor space and creates a physical barrier that can ruin the desired aesthetic of an "open" floor plan. Smoke curtains are hidden above the ceiling and only appear during an emergency, preserving the architectural intent .
### 2. Retrofitting Existing Buildings
For existing buildings undergoing renovation (Alteration Level 2), adding a lobby might be structurally impossible or prohibitively expensive. Smoke curtains offer a minimally invasive solution to bring the building up to current life safety standards without major demolition .
### 3. High-Rise Buildings
In high-rise structures, the "stack effect" is most dangerous. Curtains at each floor provide compartmentation, ensuring that a fire on the 10th floor doesn't fill the 40th floor with smoke, thus protecting occupants who may be sheltering in place .
## Installation and Maintenance Considerations
If you decide that smoke curtains are the right path for your project, there are specific installation and maintenance requirements you must follow.
1. **Compliance with NFPA 105:** The IBC code proposal G165-25 explicitly states that installation and maintenance shall be in accordance with **NFPA 105** (Standard for Smoke Door Assemblies and Other Opening Protectives) .
2. **Integration with Elevator Controls:** The curtain assembly must comply with **ASME A17.1/CSA B44** (Safety Code for Elevators and Escalators). This ensures the curtain does not interfere with the safe operation of the elevator car or the inspection procedures .
3. **Regular Testing:** Like all life safety devices, smoke curtains require periodic inspection and testing to ensure they deploy correctly and seal properly. Because they are part of the elevator maintenance program, they are subject to regular checks, which enhances long-term reliability .
## Conclusion: Lobby or Curtain?
So, are smoke curtains required at elevators? They are **required** if you choose them as your method of compliance instead of building a lobby or installing a pressurization system. With the adoption of the **2024 IBC**, smoke curtains are no longer a niche product but a fully vetted, code-compliant solution for hoistway protection .
They offer a unique blend of safety, aesthetics, and space efficiency. By containing smoke at the source and preventing the elevator shaft from becoming a chimney, these systems save lives and property. If you are designing a new building or renovating an old one, consulting with a fire protection engineer about the viability of **UL 1784-compliant smoke curtains** is a smart move that could save space and enhance safety.
