Petrochem + LPG Industrial HVAC — OISD-STD + PESO + NFPA 30 + IEC 60079 Pressurisation Framework

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MEP Consultant · Industrial / Hazardous · 11 May 2026

Petrochem + LPG Industrial HVAC — OISD-STD + PESO + NFPA 30 + IEC 60079 Pressurisation Framework

Published: 05 May 2026Updated: 11 May 2026Original figures: 9

Indian petrochem + LPG installations must meet the full OISD-STD + PESO + NFPA 30 + IEC 60079 stack. Control room HVAC sits behind Type Y barrier at +25 Pa with continuous pressurisation; analyzer shelters at Class 1 Div 2 (Zone 2) need EX-rated AHU + every cable gland EX-listed; gas detection at 25 % LEL must auto-shut HVAC + initiate purge. Mid-size petrochem control + analyzer scope runs ₹160 lakh. Three failures OISD/PESO inspectors catch: single-AHU pressurisation losing barrier during PM, analyzer shelter EX-rated with non-EX cable glands, gas-detection alarming to DCS without auto-shutdown interlock.

Petrochem + LPG industrial — the Indian regulatory stack

India petrochemical (RIL Jamnagar, IOCL Panipat, BPCL Kochi, HPCL Mahul) + LPG (HPCL bottling, IOCL Jasidih, BPCL Cherlapalli) + chemical (UPL, Pidilite, Aarti, BASF India) installations face the most stringent fire+gas regulator stack in Indian engineering — OISD-STD codes (Oil Industry Safety Directorate), PNGRB Regulations, PESO Petroleum Rules 2002, Factories Act 1948, Chemical Accident Rules 1996, IS/IEC 60079, NFPA 30, NFPA 11, API 521. Hazardous-area HVAC must combine pressurisation, purge cycles, gas-detection interlock, and intrinsically-safe design.

Petrochem control room + analyzer shelter HVAC scope

Space Hazardous classification Pressurisation Gas detection HVAC requirement
Main control room (DCS + ESD) Non-hazardous (Type Y barrier) +50 Pa positive OA intake + room EX e or non-Ex per IEC 60079; 50 Pa for Type Z
Marshalling cabinet room Type Z barrier +25 Pa positive OA intake HVAC w/ 100 % OA + filtered
Analyzer shelter (field) Class 1 Div 2 (Zone 2) +25 Pa or Type Y purge sample H2S + LEL EX-rated AHU + ducting + gas tight
Switchgear room (HV) Non-hazardous — — dust + temp control
MCC room Non-hazardous (segregated) +10 Pa — dust control + 12 ACH
Battery room (lead-acid) — — H2 detection 12 ACH continuous; spark-resistant fan
DG room (CPCB IV+) — — CO + diesel mist as per IS 9818
LPG cylinder shed Class 1 Div 1 — LPG detection natural ventilation; no electrical
Pump house (volatile) Class 1 Div 2 — LEL EX-rated lighting + motors
Tank gauge cabinets Class 1 Div 2 — — EX rated

Pressurisation + purge time for Type Z + Y barriersType Z init purge (5 vol)5minType Z continuous1minType Y init purge (10 vol)10minType Y continuous2minType X full purge (15 vol)15minType X continuous3minControl room + shelter capex (₹ lakh, mid-size petrochem)Main control room HVAC + Type Y42LMarshalling cabinet HVAC + Z28LAnalyzer shelter Z + EX-rated AHU55LMCC room + dust ctrl18LBattery room H2 detection12LLPG shed natural vent5LTotal fire+vent160L

Three petrochem HVAC failures OISD/PESO inspectors catch

  1. Control room pressurisation lost during AHU service — Type Y barrier needs continuous pressurisation per OISD-STD-163 + IEC 60079-13. AHU maintenance window must NOT depressurise the room — design with 2x AHU + auto-changeover. Indian sites routinely have single AHU + 24-hr loss-of-pressurisation during PM = barrier failure.
  2. Analyzer shelter EX-rated but cable glands non-EX — full barrier integrity needs every penetration EX-rated. Glands + sealing compounds + duct couplers — all must be Ex-d or Ex-e listed. PESO + OISD will inspect this individually. Single non-EX gland fails the entire shelter classification.
  3. Gas-detection interlock to HVAC missing — H2S or LEL alarm at 25 % must auto-stop HVAC + initiate purge. NFPA 86 + OISD-STD-163 require this. Many Indian designs alarm to DCS only without auto-shutdown — fails OISD safety audit.
// References + Standards
  1. OISD-STD-163 — Process Control Rooms + Buildings Safety, Oil Industry Safety Directorate, India.
  2. OISD-STD-189 — Standard on Fire Protection at Marketing Locations.
  3. OISD-STD-118 — Layouts of Oil + Gas Installations.
  4. NFPA 30:2024 — Flammable + Combustible Liquids Code.
  5. NFPA 11:2024 — Standard for Low- Medium- + High-Expansion Foam.
  6. API 521:2020 — Pressure-relieving + Depressuring Systems.
  7. IEC 60079 series — Explosive Atmospheres (Part 0 General + Part 13 Pressurisation + Part 14 Inspection).
  8. The Petroleum Rules 2002 (India PESO) + Petroleum + Natural Gas Regulatory Board Regulations.
  9. Chemical Accidents (Emergency Planning Preparedness + Response) Rules 1996 (India MoEF).
By MEPVAULT Editorial Team — A team of practising MEP consultants based in India. ISHRAE-affiliated; FSAI-aligned.

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