recently came up in discussion with gas trap as an example.

Circle of Protection
Incant: "I invoke Protection to create Circle of Protection."
Duration: 5 days or special
Description: This spell creates a 10-foot diameter spherical barrier, centered on the caster. This barrier will continue into the ground to complete a magical sphere around the caster, with the caster in the exact center. This barrier is frictionless and cannot be dispelled by Battle Magic spells. The Circle of Protection must be visually represented by a rope, a heavily drawn circle in the dirt, or any other method which distinctly creates a visible circle. This physical representation must be placed before the spell is cast or the spell will fail. If, during the
casting, a creature or object is on the barrier wall, the caster will decide if they are pushed out or pulled in as the Circle wall raises. After the Circle is successfully cast, no physical object may pass through the barrier, including the caster. The caster may choose to end the spell at any time. If the caster’s spirit leaves the circle for any reason, the spell will end. Once active, the Circle of Protection will act as a physical barrier preventing the passage of all
physical objects (including gas, liquid, etc.) and Battle Magic spells. This barrier functions in both directions.Gaze attacks and ritual magic will pierce through the circle as well as other powerful ritual-level effects. Multiplecastings by the same caster can be used to increase the size of the Circle by an additional 10 feet at any time after the initial Circle is cast. A Circle of Protection will not function as a ritual circle.

Gas Trap
When a Gas trap is detonated everyone within a 5 foot radius from the centre of the trap's container takes the effect of the Alchemical Gas Globe that the trap is armed with. A Gas Trap cannot be resisted by anything short of Ritual Magic or Racial Abilities. This Area of Effect trap is measured from the centre of the container. The container for this trap must be at least 100 cubic inches. With the tag for the trap you must also have 3 Alchemical gas globe tags to represent the gas in the trap. If a Gas trap is disarmed, the container still contains the gas and
may be reused but the gas inside cannot be salvaged for other Alchemy use. Gas traps and triggers are not destroyed upon detonation but the alchemy tags are used up and must be replaced

Tips for Trappers:
• Never use heavy wire for a trip lines; use fishing line
• When setting trip wires, make sure they can’t actually trip someone.
• Throwing or running with armed traps immediately sets them off
• Clean up after yourself. Do not leave trap line, old triggers, etc., in the woods. You are the smith; it is
your responsibility
• Make sure your effect tags are clearly legible and waterproofed in case of rain
• Battle Magic defenses do not protect against the Area of Effect traps

it seems to me that trap should work but a clear ruleing would be good to have.

Asked by Robert Pitchure 
Guildhouse: Jericho : Toronto Ontario