Travelling across country last night. No rain and though pitch dark on our road, blotches of orange light pollution meant we could 'see' the faraway towns.
On the far horizon was what looked like a cloud down to the tops of the hills. Given the orange lighting from the towns, the cloud looked a bit like a raincloud on that far distant hill.
Then all at once I felt as if the sides of my throat were closing together and I couldn't make a swallowing movement to clear it. As if I eaten a lump of sausage and it had got stuck half way.
Immediately I took the Ventolin from my bag and took a puff, waited half a minute and took another puff, then a minute later one more, etc. In all I had five before I was able to do a kind of silent gag reflex - as if I was making myself sick (which fortunately I wasn't or it would have been all over the car). Then as quickly as it had started, all became clear again.
Meanwhile my husband continued to drive calmly but rather more fast up the road towards civilization. We turned a corner and there ahead of us, though still on the horizon, we could see the cloud was smoke belching out from a line of factory chimneys. We estimated we were some 30 miles away from that smoke and yet with clear countryside around, seemed to be the only thing that could have affected me. Cos fields, fertilizers and animals, don't.
Guess I've found another trigger - factory smoke from miles away. Could have been an oil refinery if my geography is correct.