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Accident Report Detail

Building Explosion and Fire

Executive Summary

​On August 10, 2016, at 11:51 p.m., eastern daylight time, a 14-unit apartment building, located at 8701 Arliss Street, in the unincorporated community of Silver Spring, in Montgomery County, Maryland, partially collapsed due to a natural gas-fueled explosion and fire.

The explosion and fire also heavily damaged an adjacent apartment building, 8703 Arliss Street, which shared a common wall with building 8701.

As a result of this accident, 7 residents died, 65 residents were transported to the hospital, and 3 firefighters were treated and released from the hospital. The damage from the accident exceeded $1 million.
The following are safety issues in this accident:
  • the location and inspection of service regulators within a structure
  • the inspection of the gas meter assembly
  • the notification of the natural gas odor to Washington Gas Light Company
  • the detection of natural gas through odorants and methane


Probable Cause

​The National Transportation Safety Board determines that the probable cause of the explosion in building 8701 of the Flower Branch apartment complex was the failure of an indoor mercury service regulator with an unconnected vent line that allowed natural gas into the meter room where it accumulated and ignited from an unknown ignition source. Contributing to the accident was the location of the mercury service regulators where leak detection by odor was not readily available.

Accident Location: Silver Spring , MD    
Accident Date: 8/10/2016
Accident ID: DCA16FP003

Date Adopted: 4/24/2019
NTSB Number: PAR-19-01
NTIS Number: PB2019-100722