ZIP 01821 recorded 187 fire and hazmat incidents in 2025, 1,246 across 2021–2025. Primary county: Middlesex County, MA. FEMA NRI rates wildfire risk here as High.
1,246 incidents from 2021 through 2025 inside this ZIP.
| Year | Incidents | |
|---|---|---|
| 2021 | 292 | |
| 2022 | 203 | |
| 2023 | 283 | |
| 2024 | 281 | |
| 2025 | 187 |
Sep peaks. Feb dips. Aggregated across all 5 years inside this ZIP.
Top 5 NFIRS incident types for ZIP 01821 across 2021–2025.
| # | Incident type | Count | Share | |
|---|---|---|---|---|
| 1 | Unauthorized burning | 220 | 17.7% | |
| 2 | Gas leak (natural gas or LPG) | 212 | 17.0% | |
| 3 | Carbon monoxide incident | 122 | 9.8% | |
| 4 | Electrical wiring/equipment problem, other | 105 | 8.4% | |
| 5 | Power line down | 63 | 5.1% |
For the 7 building fires reported here in 2025, here's how investigators classified ignition cause.
NFIRS Area of Origin for ZIP 01821 fires across 2021–2025.
| # | Area of origin | Count | Share | |
|---|---|---|---|---|
| 1 | Undetermined | 59 | 26.1% | |
| 2 | Outside area, other | 32 | 14.2% | |
| 3 | Engine area, running gear, wheel area | 24 | 10.6% | |
| 4 | Wildland, woods | 15 | 6.6% | |
| 5 | Other | 13 | 5.8% | |
| 6 | Highway, parking lot, street: on or near | 13 | 5.8% | |
| 7 | Cooking area, kitchen | 11 | 4.9% | |
| 8 | Vehicle area, other | 9 | 4.0% | |
| 9 | All other areas | 50 | 22.1% |
NFIRS HEAT_SOURC code — the physical thing that started the fire.
| # | Heat source | Count | Share | |
|---|---|---|---|---|
| 1 | Undetermined | 137 | 60.6% | |
| 2 | Heat from powered equipment, other | 19 | 8.4% | |
| 3 | Hot ember or ash | 17 | 7.5% | |
| 4 | Heat source: other | 13 | 5.8% | |
| 5 | Hot or smoldering object, other | 12 | 5.3% | |
| 6 | Arcing | 7 | 3.1% | |
| 7 | Heat spread from another fire, other | 6 | 2.7% | |
| 8 | Radiated, conducted heat from operating equipment | 5 | 2.2% | |
| 9 | All other sources | 10 | 4.4% |
Largest single-incident losses in ZIP 01821 across 2021–2025. These 8 fires alone account for 3024% of the ZIP's 2025 reported total.
| # | Property loss | Type | Year | Severity |
|---|---|---|---|---|
| 1 | $5,000,000 | Gasoline or other flammable liquid spill | 2023 | Catastrophic |
| 2 | $2,000,000 | Building fires | 2023 | Major |
| 3 | $900,000 | Building fires | 2024 | Major |
| 4 | $500,000 | Building fires | 2023 | Major |
| 5 | $250,000 | Off-road vehicle or heavy equipment fire | 2022 | Major |
| 6 | $250,000 | Building fires | 2023 | Major |
| 7 | $200,000 | Building fires | 2021 | Significant |
| 8 | $200,000 | Building fires | 2021 | Significant |
Some ZIPs span multiple cities. Ranked by 5-yr NFIRS incidents inside ZIP 01821.
| # | City | 5-yr incidents | |
|---|---|---|---|
| 1 | Billerica | 1,243 | |
| 2 | Bedford | 1 | |
| 3 | Lowell | 1 | |
| 4 | Somerville | 1 |
The figures above are historical. For today's air quality, fire-weather warnings, and active fires, go to the official sources.
NFIRS reports each fire incident with a 5-digit address ZIP. We aggregate those rows directly to produce ZIP-level totals — 1,246 incidents in this ZIP across 2021–2025. Building-fire breakdowns (Area of Origin, Heat Source, ignition cause) only count fires investigators classified beyond the basic incident report. Because NFIRS reporting is voluntary, totals are a strong indicator rather than a complete census.