Does adding mesh to the vent outlet increase the risk of DDT (Deflagration to Detonation Transition) if hydrogen ignites?

All vent stacks/systems should be bonded and grounded to minimize ignition sources. Higher pressure streams from higher velocities have a greater risk of igniting for several reasons, including particle impingement. Adding mesh could create more impact points for particulate, which would increase the potential for ignition, but would not increase the probability of a DDT. Similarly, high flow releases at high pressure can create supersonic flow leading to a shock wave. While this shock wave may be sufficient to ignite the hydrogen, mesh on the outlet will not create the conditions for a DDT.

Mesh must also be designed for substantial flow area to minimize backpressure on the venting system.

Instead of mesh, the outlet of the vent systems can include small diameter stainless steel bar (for example 1/8” – 1/4”), that does not add much turbulence and applied backpressure.