Apparatus and process for securing a grating over an atmospheric opening of a ventilation shaft fluidly communicating through the ventilation shaft to an underground ventilation duct. A vertically extending support for arrangement in the shaft has horizontal flanges for projecting across a top of at least two opposing sides of said shaft to hang said support in said shaft for over topping by said grating. An anchoring member is supported in the support at a level below the flanges and proximate the atmospheric opening. A hold-down connects to the anchoring member to secure the hold-down and the grating to the anchoring member.

Apparatus and process for securing a grating over an atmospheric opening of a ventilation shaft fluidly communicating through the ventilation shaft to an underground ventilation duct. A vertically extending support for arrangement in the shaft has horizontal flanges for projecting across a top of at least two opposing sides of said shaft to hang said support in said shaft for over topping by said grating. An anchoring member is supported in the support at a level below the flanges and proximate the atmospheric opening. A hold-down connects to the anchoring member to secure the hold-down and the grating to the anchoring member.