This past weekend my husband and I were rock hunting a county road cut near Bandera. This is a rural road with the occasional car going by but no real traffic.

About an hour into or search we both began to feel tired, nauseous and got headaches. We were both struck by these symptoms very quickly. Our legs became weak and we got dizzy. At first we didn't know the other was feeling the same way until my husband said he didn't feel well. I told him I didn't either and described what was happening. We both retreated to the truck and sat down.
After about ten minutes we both felt better with just lingering headaches. We went back to rock hounding for another hour with no other problems.
Later we wondered if some sort of natural emission of odorless gas had hit us. Do these things happen?
Any ideas?

About an hour into or search we both began to feel tired, nauseous and got headaches. We were both struck by these symptoms very quickly. Our legs became weak and we got dizzy. At first we didn't know the other was feeling the same way until my husband said he didn't feel well. I told him I didn't either and described what was happening. We both retreated to the truck and sat down.
After about ten minutes we both felt better with just lingering headaches. We went back to rock hounding for another hour with no other problems.
Later we wondered if some sort of natural emission of odorless gas had hit us. Do these things happen?
Any ideas?
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