Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Notes on this paper
National Exams — May 2016 — 11-CS-2 Engineering in Society: Health and Safety. Closed book; approved calculator permitted. Any five of the seven questions constitute a complete paper; all questions are of equal value. Answers are written in point form but fully, as instructed. Complete answers to all seven questions follow.
Question 4: Fire Detection and Suppression (20 marks: 6/7/7)
(a) Heat detectors — respond to temperature (fixed-temperature or rate-of-rise); reliable with few false alarms but slower; suited to dirty/dusty areas.
(b) Smoke detectors — respond to combustion products (ionization = fast flaming fires; photoelectric = smouldering fires); faster early warning but more prone to false alarms in dusty/steamy areas.
(ii) Sprinkler Systems
(a) Wet-pipe — pipes always hold water; immediate discharge when a head opens; simplest/most reliable; not for freezing areas.
(b) Dry-pipe — pipes hold pressurized air; water admitted when a head opens; for unheated/freezing areas; slight delay.
(c) Deluge — all heads open; a detection system opens the deluge valve so water flows from every head at once; for high-hazard, rapid, large-area needs.
(iii) Non-Water Suppression Systems
Used where water is ineffective/damaging (electronics, flammable liquids). Extinguish by removing a leg of the fire tetrahedron: clean agents/gaseous (inert gas/halocarbon—no residue), CO₂ (smother by oxygen displacement—asphyxiation hazard), dry chemical (interrupt the reaction), foam (blanket flammable-liquid surfaces). Selection depends on fire class, contents and occupant safety.
