Explosion Mitigation Manhole Solution

Explosion mitigation manhole access assembly open with fire and smoke in manhole

Keep your underground power networks covered and secure.

The Problem

Electrical or gas explosions inside an underground utility vault can happen without warning. In these situations, a standard, unrestrained manhole cover can potentially become a dangerous projectile.

The Solution

The explosion mitigation manhole assembly (EM3) is designed to relieve built up pressure while restraining the cover during an explosive event and then return to the seated position after the pressure returns to normal.

The cover tilts when there is an underground explosive event. "Directed venting" minimizes path of harmful hot gases. 

Explosion Mitigation manhole cover rendering shown closed and in the open position venting

Explosion mitigation manhole covers installed in roadway

Standard Features

  • Light weight ductile iron cover
  • Heavy duty H-25 load application
  • Meets AASHTO M306-10 requirements
  • Can be used in a retrofit application
  • Ergonomic slide rails for easy removal
  • Machined seat
  • Cast-in bolt holes for securing frame to structure
  • Available in sizes ranging from 20" to 40" clear opening – other sizes available upon request
  • Made in the USA


  • Security bolt for controlled access and theft deterrent
  • Custom logo covers
  • Special lettered covers
  • Frame with angled anchor rods
  • Frame with centering ring on bottom
  • Vented covers and grated versions available

Operation Demonstration Video

Testing Demonstration Video

Learn More

Talk to an expert at EJ to find out how the innovative solutions by EJ can work for your next project. Contact us today or schedule a Lunch and Learn.

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