Door Lock Monitoring, or DLM, is a critical elevator safety feature specified in ASME A17.1/A17.3 codes. It ensures that elevators cannot move unless the car doors are fully closed—and that no faulty or bypassed circuits can override safety systems.
In technical terms, DLM uses sensors and logic circuits to:
1. Prevent car movement if the car doors aren’t fully sealed—even if the interlock signals appear OK.
2. Stop automatic door-close operations if circuits are shorted or bypassed while doors are fully open
Safety & Code Requirements
ASME A17.1–2000 onward introduced mandatory DLM language. Since then, retrofit requirements under A17.3-2015 apply to all existing elevators
Many U.S. jurisdictions (Florida, New York, Minnesota, Washington, Nevada, Georgia, South Carolina, and more) have adopted DLM enforcement. For instance:
· Florida: All elevators must have DLM by January 1, 2024, or face fines/shutdowns
o https://www.flsenate.gov/Session/Bill/2017/01634
o http://www.leg.state.fl.us/statutes/index.cfm?App_mode=Display_Statute&Search_String=&URL=0300-0399%2F0399%2FSections%2F0399.031.html
· New York City: Compliance has been mandatory since January 1, 2020 .
o https://www.nyc.gov/assets/buildings/pdf/Elevators_DLM_Energy_Code_Compliance.pdf?utm_source=chatgpt.com
· Minnesota: Inspections began in 2021, with 60-day penalty-free compliance plans allowed .
Why this matters:
At a high level it prevents injuries or fatalities caused by car movement with open doors.
What Does a Building Encounter When Implementing DLM?
1. Assessing Existing Infrastructure
· Elevators built/modernized after 2000 often have DLM hardware but it may not be activated.
· Older units may lack sensors, logic boards, or use outdated wiring
A professional inventory survey or if the building can provide enough data an opinion can confirm compliance and identify upgrade needs
2. Selecting the Solution
· Activate existing DLM via software or parameter changes if equipment already supports it.
· Add a universal overlay from a supplier to retrofit compliance
· Full modernization upgrading the control panel, sensors, door operator, etc. for older systems without DLM capability maybe necessary.
3. Timeline & Cost
· Activation or overlay: potentially completed in days with minimal downtime.
· Modernization: may take weeks and cost tens of thousands, especially for older equipment
· Costs range from a few thousand dollars to several tens of thousands of dollars or more depending on scope and whether full replacement is necessary
4. Permitting & Inspection
· Permits are often mandatory (e.g., NYC, Florida) .
· Authority Having Jurisdiction Inspectors confirm DLM functions per ASME A17.3
· Violations can trigger penalties, elevator shutdowns, or requirement of a compliance plan
Why Work with a Professional Elevator Consultant?
Professional elevator consulting firms like The Elevator Consultants provide essential expertise for navigating the DLM maze:
· Unbiased code analysis: Confirm whether your building needs door lock monitoring, or if it simply requires activation of existing features.
· Cost-effective solution selection: Evaluate activation, overlay, or full modernization based on life cycle planning and building goals.
· Accurate bidding: Avoid blanket proposals that could overcharge by tens of thousands
· Seamless coordination: Handling the entire project if needed from scope to final inspection, and contractor oversight.
· Risk mitigation: Ensure passenger safety, compliance, and prevent downtime/disruptions.
Best Practices for Implementation
1. Start with an inspection to inventory DLM readiness.
2. Review your jurisdiction’s compliance deadline, and whether a grace or planning period applies.
3. Compare options—activation vs. overlay vs. modernization based on cost, elevator age, usage, and future plans.
4. Engage a professional elevator consultant to oversee specification, bid-process, and installation fidelity.
Door Lock Monitoring isn’t a luxury it’s a code-mandated, life-saving requirement. Whether your elevator has outdated logic or lacks basic sensors, converting that gap into compliance ensures safety, legal protection, and reliability.
As a seasoned elevator consulting firm like The Elevator Consultants, we help anyone with an elevator from building owners, facility managers, and hotel or hospital operators through detailed assessments, specification writing, and installation oversight. We ensure each DLM project is code-compliant, budget-aligned, and seamlessly integrated into your vertical transportation system.
Need help with door lock monitoring (DLM)?
Reach out to The Elevator Consultants for a no-obligation assessment and customized elevator management plan.
What is Door Lock Monitoring (DLM) in elevators?
Door Lock Monitoring (DLM) is a safety feature required by elevator code (ASME A17.3) that prevents an elevator from moving unless its doors are fully closed and locked.
2. Why is DLM required?
DLM is mandated to prevent dangerous situations where an elevator moves with open or improperly secured doors. It’s a life-safety feature enforced by updated building codes to protect passengers and minimize legal liability for property owners.
3. Is DLM required in all U.S. states?
No, but it’s rapidly being adopted. States like Florida, New York, and Minnesota have already mandated DLM with specific compliance deadlines. Many others are expected to follow suit based on ASME A17.3 adoption.
4. What’s the deadline for DLM compliance in Florida?
Florida’s compliance deadline was originally December 31, 2023, but has been extended to August 1, 2025. All elevators must have DLM installed and operational by this date to avoid fines and potential shutdowns.
How do I know if my elevators already have DLM?
Elevators installed or modernized after 2000 may already have DLM hardware but not be activated. A professional elevator consultant can perform an audit to verify compliance and determine the best course of action.
What are the options for installing DLM?
· Activate existing systems if hardware is compatible.
· Install a retrofit DLM overlay unit if current systems can’t support it.
· Modernize the elevator control system entirely for older or obsolete units
This depends on the elevator system installed.
How much does it cost to comply with DLM requirements?
Costs can vary based on the equipment installed from a few thousand for a simple activation to tens of thousands or more if a full modernization. Factors include elevator age, manufacturer, number of floors, and control system type.
Will DLM installation cause elevator downtime?
Minimal downtime is expected for overlays or activations often just hours or a few days. However, full modernizations can take weeks and months. Proper project management by an elevator consultant helps minimize disruption.
Can building owners face penalties for non-compliance?
Yes. Jurisdictions like NYC and Florida impose fines, failed inspections, and even elevator shutdowns for non-compliance. Insurance carriers may also deny claims if a non-compliant elevator causes injury.
Who should I contact to get started with DLM compliance?
Engage a professional elevator consulting firm like The Elevator Consultants. They provide a full plan for you based on the number or elevators and your situation from a simple call to expert inspections, compliance strategies, project oversight, and contractor coordination to ensure full, code-compliant execution.