Firefighters were called to two adjacent apartment buildings on North Summit Avenue in Gaithersburg Saturday morning after crews found high levels of carbon monoxide inside, sickening several residents and sending at least two people to the hospital. Montgomery County Fire and Rescue Service first responders were dispatched at 8:44 a.m., according to fire officials.
Crews found elevated carbon monoxide levels at 422 North Summit Avenue and officials also reported high readings next door at 420 North Summit Avenue, according to WJLA. The reported gas leak at 422 North Summit Avenue involved multiple sick people, and crews began evaluating residents from both buildings for possible transport to area hospitals.
Fire officials initially reported five people were being evaluated, though that number later grew as crews continued assessing residents; the station's report indicates eight people from 422 North Summit Avenue were ultimately being evaluated. At least two of those residents were taken to the hospital, and the hospitalized individuals are expected to survive, per the same account. The cause of the gas leak remained undetermined as crews continued investigating.
A Pattern of Carbon Monoxide Emergencies Across the County
Saturday's incident adds to a string of carbon monoxide scares that have rattled Montgomery County in recent months. In August, MCFRS crews evacuated a seven-story residential building and an adjacent bank branch on Woodmont Avenue in Bethesda after gas leak meters registered high carbon monoxide levels inside, according to Daily Voice; that response also came after occupants reported feeling sick inside the building. And in a separate incident, an elderly couple in nearby Boyds died from carbon monoxide poisoning after levels inside their home reached 2,000 parts per million, a concentration 400 times higher than normal indoor baseline levels, caused by a vehicle left running in an attached garage, WUSA9 reported. In that case, MCFRS responders noted the home's alarm had initially been mistaken for a smoke detector.
These incidents track with a broader statewide surge. Emergency room and urgent care visits for carbon monoxide exposure in Maryland reached 251 cases in early 2026, a nearly 50% jump from the 167 cases recorded statewide in all of 2025, according to CBS News. The report attributed winter spikes in exposure to alternative heating sources and combustion. Separately, Maryland recorded 234 emergency department and urgent care visits for carbon monoxide exposure during the 2025–2026 winter cold season, the highest seasonal total in six years, according to state health data cited by Maryland Matters.
What the Law Requires of Landlords
Montgomery County rules require carbon monoxide alarms on every level and outside sleeping areas in many existing residential dwellings, a requirement that took effect in July 2019, per Montgomery County government records. Maryland law separately sets installation and operating requirements for carbon monoxide alarms in rental dwellings, with rental alarms required to be hardwired with battery backup or use long-life sealed 10-year batteries, according to the Maryland People's Law Library.
The Montgomery County Department of Housing and Community Affairs Housing Code Enforcement Unit inspects rental properties. The available WJLA account does not specify how tenants can report noncompliant carbon monoxide alarms or discuss whether the North Summit Avenue buildings met those code requirements, and the exact mechanical failure behind Saturday's elevated readings remains undetermined.
Why Carbon Monoxide Is So Dangerous
Inhaled carbon monoxide displaces oxygen in the bloodstream by binding to hemoglobin, triggering symptoms including headache, dizziness, weakness, nausea, confusion and loss of consciousness, according to the Centers for Disease Control and Prevention. Initial symptoms can be mild. Nationally, carbon monoxide poisoning causes more than 400 deaths annually in the United States.
North Summit Avenue has seen fire crews respond before; in March 2023, MCFRS firefighters extinguished a third-floor exhaust fan fire in a multi-family building on the same block, temporarily displacing one resident family, according to The MoCo Show. Saturday's carbon monoxide response remains a developing story, and Montgomery County Fire and Rescue Service is expected to release more information as the investigation into the leak's cause continues.
