WORD SPIRAL

Starting from 1, fill in the grid clockwise with four-letter words. The last letter of each word becomes the first letter of the next to reveal a Flammable gas.

1. Facial disguise 2. Slay 3. Citrus fruit 4. Simple 5. Egg part 6. Hit with the foot 7. Retain 8. Bucket 9. Produces eggs 10. Glance at quickly 11. Midday 12. Undiluted 13. Dense layer of grass 14. Amphibian 15. Long deep cut 16. Rigid circular band