Kitchen Exhaust System Design for Hotel F&B — NBC and NFPA Guide

Hotels & Hospitality

Kitchen Exhaust System Design for Hotel F&B — NBC and NFPA

Commercial kitchen exhaust design is one of the most demanding and safety-critical MEP tasks in hotel projects. Get it wrong and you face fire risk from grease accumulation, odour complaints from guests, regulatory non-compliance, and potential kitchen closure. This article covers the complete design process from hood sizing through to fire suppression.

1. Governing Standards

Standard	Scope	Authority
NBC 2016 Part 4	Kitchen fire safety, exhaust requirements	BIS / MoHFW — mandatory India
NFPA 96	Commercial cooking ventilation and fire protection — comprehensive	NFPA — widely adopted in India for 4-star+
IS 1646	Fire safety in buildings — kitchen references	BIS — baseline Indian standard
ASHRAE 154	Ventilation for commercial cooking operations	ASHRAE — referenced by designers
Brand standards	Specific to hotel brand (Marriott, Hilton etc.)	Brand operator — often most detailed

2. Kitchen Hood Types and Selection

Hood Type	Description	Application	Capture Efficiency
Type I (grease)	Captures heat, grease, vapours — full steel construction	Over all grease-producing equipment	High — required for frying, grilling
Type II (heat/steam)	Captures heat and steam only — no grease filter	Over dishwashers, ovens, steamers	Moderate
Compensating hood	Supplies make-up air directly through hood	When separate make-up air unit not practical	High
Proximity hood	Mounted close to cooking surface	Where ceiling height is limited	Very high — less exhaust needed

3. Hood Sizing — Exhaust Flow Rate Calculation

Method 1 — Overhang Factor Method (NFPA 96 / ASHRAE 154)

Exhaust flow rate (L/s) = Hood length (m) × Hood depth factor × Cooking intensity factor × 100

Cooking Equipment	Exhaust Rate (L/s per m of hood length)	Notes
Fryers (heavy duty)	350–500	Highest grease and heat load
Griddles, charbroilers	300–450	High grease production
Wok burners	400–600	Very high heat + vapour
Ranges / cooking tops	250–350	Moderate
Ovens (standard)	150–250	Lower — mostly heat
Steamers / combi ovens	100–200	Steam — Type II hood
Dishwashers	100–150	Steam only — Type II

4. Grease Filter Selection

Filter Type	Efficiency	Maintenance	Best For
Mesh filters (aluminium)	60–70%	Weekly cleaning	Light duty kitchens
Baffle filters (stainless)	75–85%	Weekly cleaning	All commercial kitchens — standard
High-efficiency cartridge	90–95%	Monthly replacement	High-volume 5-star kitchens
Ultraviolet (UV) grease removal	95%+ with UV	Monthly lamp replacement	Premium — reduces duct grease buildup significantly

5. Exhaust Duct Design Requirements — NFPA 96

Duct material: minimum 1.6 mm (16 gauge) stainless steel or carbon steel — no aluminium for Type I
Velocity: minimum 7.5 m/s (1500 ft/min) to prevent grease fallout in horizontal runs
Slope: minimum 1:50 toward a grease collection point
No bends less than 45° — smooth radius only
Access panels: every 3–4 m on horizontal runs and at every change of direction
Clearance to combustibles: 150 mm (6 inches) for listed duct systems
Duct penetrations through fire-rated walls: fire dampers not permitted in grease ducts — use listed wall penetration system

6. Make-Up Air Requirements

Make-up air must replace 80–100% of the exhaust volume to prevent negative pressure in the kitchen. Under-provision of make-up air is the single most common cause of poor kitchen exhaust performance in Indian hotels.

Supply 80–90% of exhaust as make-up air — remaining 10–20% from dining area infiltration maintains slight negative pressure in kitchen
Temperature of make-up air: 18–22°C — tempered in summer, not over-cooled
Introduce make-up air from perimeter of hood at low velocity to avoid disrupting capture
In Indian monsoon climate — dehumidify make-up air to prevent condensation on cold food surfaces

7. Fire Suppression System — NBC and NFPA 96

Automatic fire suppression required in all Type I hoods in 4-star and above (NBC Part 4 + NFPA 96)
Wet chemical systems (Class K) — most common in India (Ansul, Amerex, Kidde brands)
Nozzle placement: above each cooking appliance + within duct plenum
System must link to: gas isolation valve (auto shutoff), exhaust fan (continue running), make-up air fan (shut off)
Monthly visual inspection + 6-monthly service by licensed contractor

Kitchen Exhaust System Design for Hotel F&B — NBC and NFPA Guide