An ignition-quenching cover such as a cover for a metal fastener in a composite fuel tank in an aircraft, configured to quench an ignition event in a combustible environment, such as the fuel in the tank, the ignition event triggerable by an ignition source, such as an electrical arc, a hot surface, a hot particle ejection, and/or an electrostatic discharge, associatable with an ignition-risk structure, such as the metal fastener, the ignition-quenching cover comprising: a porous body that includes a combination of two or more porous elements; wherein the porous body and porous elements each include a plurality of pores and a plurality of struts which struts are structural components that adjoin and/or define the pores, the ignition-quenching cover being configured to cover the ignition-risk structure, wherein the ignition-risk structure is associated with a potential ignition source that may produce the ignition event in the combustible environment, wherein the porous body defines passages sized to quench the ignition event, which passages are straight line passages, and wherein the porous body defines a cavity that is configured, sized and/or shaped to receive the ignition-risk structure, wherein the ignition-quenching cover has a proximal cover side and a distal cover side, the proximal cover side configured to face the ignition-risk structure, the distal cover side opposite the proximal cover side, wherein the two or more porous elements are foams and/or lattices that lack a straight-line open path connecting the proximal cover side and the distal cover side in order to prevent a hot particle of greater than a predetermined size associated with the ignition source from passing through the porous body along a straight line trajectory, wherein a passage orientation of at least one of the two or more porous elements is different than a passage orientation of at least another of the two or more porous elements, wherein each porous element individually has the straight-line passages therethrough, whereby the combination of porous elements at different passage orientations results in the lack of a straight-line open path connecting the proximal cover side and the distal cover side through the porous body. a porous body that includes a combination of two or more porous elements; wherein the porous body and porous elements each include a plurality of pores and a plurality of struts which struts are structural components that adjoin and/or define the pores, the ignition-quenching cover being configured to cover the ignition-risk structure, wherein the ignition-risk structure is associated with a potential ignition source that may produce the ignition event in the combustible environment, wherein the porous body defines passages sized to quench the ignition event, which passages are straight line passages, and wherein the porous body defines a cavity that is configured, sized and/or shaped to receive the ignition-risk structure, wherein the ignition-quenching cover has a proximal cover side and a distal cover side, the proximal cover side configured to face the ignition-risk structure, the distal cover side opposite the proximal cover side, wherein the two or more porous elements are foams and/or lattices that lack a straight-line open path connecting the proximal cover side and the distal cover side in order to prevent a hot particle of greater than a predetermined size associated with the ignition source from passing through the porous body along a straight line trajectory, wherein a passage orientation of at least one of the two or more porous elements is different than a passage orientation of at least another of the two or more porous elements, wherein each porous element individually has the straight-line passages therethrough, whereby the combination of porous elements at different passage orientations results in the lack of a straight-line open path connecting the proximal cover side and the distal cover side through the porous body.