Introduction
The U.S. battery energy storage system (BESS) market is experiencing unprecedented growth, with installed capacity projected to reach a twenty-fold increase in just five years. Yet alongside this rapid expansion, the industry has faced a sobering reality. Lithium-ion battery fires are notoriously difficult to control, and a single thermal runaway event can result in millions of dollars in property damage, project delays, and reputational harm.
This is where the Hazard Mitigation Analysis (HMA) becomes indispensable. As Angelo Zandona has emphasized throughout his career in fire and life safety engineering, an HMA, mandated under NFPA 855, is far more than a regulatory checkbox. It is the foundational risk document that informs every downstream decision in a BESS project, from site layout and setback distances to emergency response protocols and water supply requirements.
For Engineering, Procurement, and Construction (EPC) firms, battery manufacturers, and general contractors building large-scale storage facilities, understanding the HMA process is crucial. This article breaks down what an HMA is, why it matters, what it contains, and how a well-prepared analysis can save months of permitting delays and significantly reduce project risk.
What Is a Hazard Mitigation Analysis?
A Hazard Mitigation Analysis is a structured engineering document that identifies potential failure scenarios in a battery energy storage system, evaluates their consequences, and prescribes mitigation measures to reduce risk to acceptable levels. It is required under Section 4.1.4 of NFPA 855 for most stationary energy storage installations exceeding specific capacity thresholds.
Unlike a generic risk assessment, an HMA is highly technical and site-specific. It must address chemistry-specific hazards (lithium iron phosphate behaves differently than nickel manganese cobalt, for example), environmental conditions, system architecture, and the capabilities of local emergency responders. The document is submitted to the Authority Having Jurisdiction (AHJ) as part of the permitting process. A properly executed HMA accomplishes three primary objectives:
- Identification of credible failure modes specific to the proposed system
- Evaluation of the consequences of those failures, including thermal runaway propagation
- Mitigation through engineered controls, operational procedures, and emergency response planning
Why HMAs Became Mandatory
To understand why HMAs are now central to BESS deployment, it helps to look at the recent history of the industry.
Between 2018 and 2023, the energy storage industry experienced several high-profile fire incidents at large-scale BESS facilities. Early projects relied heavily on traditional fire protection strategies that proved inadequate against lithium-ion thermal runaway. In multiple cases, suppression systems either failed to extinguish fires or, worse, created explosive atmospheres that endangered first responders.
The fire protection community, led by the National Fire Protection Association, recognized that a new framework was needed. Traditional prescriptive codes could not keep pace with rapidly evolving battery chemistries and system designs. A performance-based approach was required, one that placed the burden on project developers to demonstrate that their specific system, in its specific location, would behave safely under foreseeable failure conditions.
NFPA 855 was published in 2020 and has been updated in subsequent editions. The standard requires an HMA for most installations and provides a framework for evaluating hazards including thermal runaway, off-gas generation, deflagration, electrical faults, and external events such as flooding or seismic activity.
Today, the HMA serves as the primary technical document AHJs use to determine whether a BESS project meets the intent of the code. Projects with thorough, well-supported HMAs move through permitting in weeks and those with deficient analyses can face months of revisions, redesigns, and lost revenue.
What Does an HMA Actually Contain?
While the specific contents vary by jurisdiction and project scope, a comprehensive HMA typically includes the following sections.
- System Description: A detailed overview of the BESS, including battery chemistry, capacity (in MWh), enclosure design, electrical configuration, and the manufacturer’s certifications. This section establishes the baseline conditions against which hazards will be evaluated.
- Site Context and Adjacent Exposures: The analysis must account for what surrounds the installation. Is the site adjacent to occupied buildings? Critical infrastructure? Wildland vegetation? The proximity of these exposures directly influences setback requirements and mitigation strategies.
- Hazard Identification: This is the analytical heart of the document. The author identifies credible failure scenarios and traces their potential consequences.
- UL 9540A Test Data Integration: NFPA 855 requires that HMAs incorporate data from large-scale fire testing conducted under UL 9540A. These tests, conducted at unit, module, and installation levels, provide empirical data on heat release rates, flammable gas generation, and propagation behavior. The HMA translates this test data into site-specific recommendations.
- Mitigation Measures: For each identified hazard, the HMA prescribes specific controls. These may include physical separation distances, deflagration venting per NFPA 68, explosion prevention systems per NFPA 69, gas detection, deluge water systems for exposure protection, and emergency shutdown procedures.
- Emergency Response Considerations: The HMA must demonstrate that the proposed mitigations are compatible with the capabilities of the local fire department. A site forty-five minutes from the nearest fire station requires different controls than one in an urban area.
Who Needs an HMA?
Under current NFPA 855 thresholds, an HMA is required for most stationary energy storage installations above 20 kWh for residential systems and significantly lower thresholds for commercial and utility-scale projects.
- Utility-scale BESS developers building grid-tied storage paired with solar or wind
- Battery manufacturers seeking to deploy their products in regulated jurisdictions
- EPC contractors managing the design and installation of energy storage facilities
- Commercial and industrial facility owners integrating behind-the-meter storage
- Data center operators deploying large backup storage systems
Even projects in jurisdictions that have not formally adopted NFPA 855 increasingly require HMAs as a matter of best practice, particularly when seeking insurance coverage or financing.
The Real Cost of Skipping or Skimping on an HMA
It is tempting for project developers under tight timelines to view the HMA as a procedural hurdle. As Angelo Zandona often points out to clients, this is a costly mistake.
According to research from the Electric Power Research Institute (EPRI), permitting and interconnection delays now represent one of the largest sources of cost overrun in utility-scale storage projects, with some developers reporting delays of six to twelve months attributable to inadequate safety documentation. For a 100 MWh project generating revenue through capacity payments and energy arbitrage, a six-month delay can translate into millions in lost income.
A weak HMA also increases the likelihood of post-construction modifications. If an AHJ identifies deficiencies after equipment is installed, the cost of retrofitting deflagration vents, expanding water storage, or adding gas detection can be ten to twenty times higher than addressing the same issues at the design phase.
What Separates a Strong HMA From a Weak One?
Drawing from more than two decades in fire and life safety, Angelo Zandona has worked on everything from data centers and power generation facilities to large-scale battery storage, and certain patterns emerge in what distinguishes effective hazard analyses.
- Strong HMAs are site-specific: They reflect the actual project layout, climate, and adjacent exposures rather than relying on generic templates. AHJs can immediately tell when a document has been copied from a prior project with names changed.
- Strong HMAs integrate current test data: UL 9540A reports are evolving rapidly as battery chemistries change. An HMA referencing outdated test data signals to the AHJ that the analysis is incomplete.
- Strong HMAs demonstrate AHJ collaboration: The most successful projects, in Angelo Zandona‘s experience, involve early engagement with the local fire marshal, often before the formal submittal. This allows the consultant to understand jurisdiction-specific concerns and tailor the document accordingly.
- Strong HMAs are written for the reader: Fire marshals are technically sophisticated but pressed for time. A well-organized document with clear executive summaries, defensible conclusions, and traceable reasoning moves through review far faster than a dense technical report that forces the reviewer to hunt for key information.
The HMA’s Relationship to Other Required Documents
The HMA is one of several technical documents that together form the safety case for a BESS project. These typically include:
- Emergency Response Plan (ERP): Operational guidance for first responders during an incident
- Water Supply Analysis: Quantitative justification for on-site water storage requirements
- Failure Modes and Effects Analysis (FMEA): A systematic look at component-level failure pathways
- NFPA 68/69 Deflagration Analysis: Specific evaluation of explosion hazards and prevention measures
Conclusion
The Hazard Mitigation Analysis is the technical foundation on which safe, permittable, and insurable battery energy storage projects are built. As the BESS industry continues its rapid expansion, the quality of HMA documentation will increasingly separate projects that come online on schedule from those that languish in permitting purgatory.
For developers, manufacturers, and contractors investing in this space, Angelo Zandona‘s message is to engage qualified fire and life safety expertise early, treat the HMA as a strategic asset rather than a compliance cost, and recognize that the hours spent producing a thorough analysis will be repaid many times over in faster approvals, lower insurance premiums, and reduced operational risk. In an industry where time-to-energization directly determines project economics, getting the HMA right is one of the highest-leverage decisions a project team can make.
FAQs
Is an HMA required for every battery energy storage system?
ANS: Not every system, but most commercial and utility-scale installations require one under NFPA 855. The specific threshold depends on the system’s energy capacity, the jurisdiction’s adopted code edition, and the AHJ’s discretion. Even where not strictly required, many insurers and financiers now expect an HMA as a condition of coverage or funding.
How long does it take to produce an HMA?
ANS: Timelines vary based on project complexity, but a typical utility-scale HMA takes four to eight weeks from initial engagement to final submission. Projects with unusual chemistries, complex sites, or limited UL 9540A data may take longer. Early engagement with a qualified consultant can compress this timeline significantly.
Who is qualified to prepare an HMA?
ANS: NFPA 855 requires that HMAs be prepared by qualified persons, typically interpreted as licensed fire protection engineers or fire and life safety consultants with demonstrated experience in energy storage systems. The qualifications of the author are themselves often scrutinized by the AHJ during review.
What happens if the AHJ rejects the HMA?
ANS: A rejection typically triggers a revision cycle, with the AHJ providing comments that must be addressed before resubmittal. In severe cases, fundamental design changes may be required, which can have significant cost and schedule implications.
Can the same HMA be used for multiple sites?
ANS: Generally, no. While portions of the analysis may be reused, the site-specific elements (exposures, climate, emergency response capabilities, layout) must be evaluated for each project. Attempting to submit a templated HMA across multiple sites is one of the most common reasons for AHJ rejection.
