Airport Terminal Ventilation System: Fresh Air, Filtration, ERV and IAQ

This guide connects the topic to SongXin’s airport HVAC system design guide, airport HVAC maintenance checklist, airport HVAC solutions, air-cooled screw chiller and air handling unit resources for product selection, internal linking and buyer verification.

Scope of this guide: outdoor-air quantity, filtration, ERV/DOAS, pressure zoning and IAQ operating modes. Use the broader airport HVAC system design guide for central plant architecture, terminal cooling selection and whole-system coordination.

An airport ventilation system should supply outdoor air, filter particles, recover energy, manage pressure relationships and support passenger comfort across zones with very different occupancy patterns. Departure halls, arrivals, security checkpoints, baggage areas, offices, retail spaces and lounges do not need the same airflow strategy.

The practical rule is to design ventilation by zone, not by one average terminal value. High-occupancy halls need outdoor-air capacity and filtration. Security and control areas need stability. Baggage and service areas need exhaust coordination. Energy recovery on outdoor air streams typically saves 30–50% of fresh-air conditioning energy in airport climates. AHUs need filter and coil access because maintenance is part of ventilation performance.

This guide connects terminal ventilation to SongXin’s airport HVAC system design guide, airport HVAC plant room design, airport HVAC maintenance checklist, air handling unit and comfort AHU vs process AHU resources.

An airport ventilation system should be specified by zone airflow, outdoor-air rate, filtration class, energy recovery, pressure relationship, AHU access and maintenance interval. The safest procurement approach is to list each terminal zone separately, then match AHUs, filters, fans, ERV and controls to that zone’s occupancy and operating schedule.

For many airport terminals, ventilation problems come from three causes: outdoor air is added without enough cooling and dehumidification capacity, filters are selected without fan-pressure allowance, or energy recovery is omitted leading to high OPEX. All three failures reduce comfort or energy performance because the AHU no longer delivers the designed air volume at the targeted IAQ.

Buyer’s 30-second rule:

• < 5,000 m³/h outdoor air per AHU → simple mixing box + ERV
• 5,000–20,000 m³/h per AHU → dedicated ERV section mandatory
• > 20,000 m³/h per AHU OR high-RH climate → DOAS (Dedicated Outdoor Air System) with full ERV
• High pollution / urban airport → MERV 14 / ePM1 50% as minimum
• Pandemic / IAQ-sensitive areas → HEPA H13 or higher + UV-C

ASHRAE 62.1 is the de-facto reference for airport ventilation. These are the typical per-person + per-area rates for airport-relevant occupancy categories.

Practical examples:

• Departure hall, 200 m² × 100 pax → outdoor air = 200 × 100/100 × 3.8 + 200 × 0.3 = 760 + 60 = 820 L/s ≈ 2,950 m³/h
• Food court, 500 m² × 70 pax/100 m² = 350 pax → 350 × 3.8 + 500 × 0.9 = 1,330 + 450 = 1,780 L/s ≈ 6,400 m³/h

For high-altitude airports (above 2,000 m), apply a density correction factor since ventilation is volumetric. For high-occupancy events, design to peak occupancy not nominal.

Airport ventilation should map the terminal into zones before AHU selection. Passenger density, door opening, baggage handling and security requirements change the airflow duty.

The zone map matters because a single AHU serving mixed zones can over-ventilate one area and under-ventilate another. Dedicated or well-zoned AHUs reduce that mismatch because airflow follows occupancy and schedule.

Airport terminals see high passenger density, outdoor pollution, jet exhaust, dust and baggage particulates. Filtration class affects IAQ, energy and maintenance.

Modern airport baseline (post-2020 design):

• Prefilter: Coarse 60% (MERV 8)
• Main filter: ePM2.5 80% (MERV 14) minimum
• VIP / lounges: ePM1 50–80% (MERV 14–15)
• ATC / IT rooms: ePM1 + activated carbon for VOC
• Pandemic / surge mode: HEPA H13 add-on capability

Practical rule: every filter upgrade adds 50–100 Pa pressure → fan size and energy go up. Budget the final filter pressure (not clean) in ESP. SongXin’s AHU sections support panel / bag / HEPA configurations with airtight seals and accessible service panels.^[9]

Fresh air is not free air; it adds cooling and humidity load to the terminal. Every outdoor-air decision should be paired with coil, fan and chiller capacity.

Fresh air raises cooling demand because the AHU must remove heat and moisture from outside air. In humid climates, the latent load is the hidden problem: the coil needs to condense water before the supply air reaches the target humidity.

Energy recovery on airport outdoor-air streams is one of the highest-ROI investments in terminal HVAC. With outdoor air rates of 10,000–100,000+ m³/h per AHU and 8,760 hours of annual operation, even 50% sensible-only recovery saves substantial energy.

Typical airport ERV ROI:

• Single-stage plate HX, 20,000 m³/h, 60% efficiency, hot-humid climate
• Annual fresh-air conditioning energy without ERV: ~120,000 kWh
• With ERV: ~50,000 kWh → 70,000 kWh saved/yr → ~USD 8,400/yr at USD 0.12/kWh
• Incremental ERV CAPEX: ~USD 18,000 → payback ~2.1 years

For Gulf, Southeast Asian, South Asian and tropical airports with both heat and humidity, enthalpy wheels are typically the highest-ROI choice. For dry-climate airports (Saudi inland, North Africa), sensible-only plate or heat pipe is enough.

Two main strategies exist for outdoor air integration:

Most modern large-airport designs use DOAS + zone units (FCU, VAV box, chilled beam). Departure halls keep mixed-air AHUs with VAV; small zones get DOAS + FCU. The DOAS handles 100% of latent load, simplifying zone equipment.

Pressure zoning prevents cross-contamination and odor migration. Each airport zone should have a defined relationship to adjacent zones.

Practical rule: maintain ΔP using dedicated exhaust fans (not just adjusting supply). Use pressure sensors with BMS alarms on critical zones; rebalance after major terminal changes.

Modern airports target specific IAQ KPIs:

Special operating modes:

Modern AHUs should support mode switching via BMS, including outdoor-air damper override, ERV bypass, filter override, and pressure-zone reset.

A basic calculation shows why outdoor air must be included before AHU selection. Assume an airport zone needs 10,000 m³/h of outdoor air, and the outdoor-to-indoor enthalpy difference is 18 kJ/kg (hot-humid tropical / Gulf summer condition). Air density 1.2 kg/m³.

Step 1 – Outdoor air cooling load (no ERV).

Formula: cooling load = airflow × air density × enthalpy difference / 3600. Substitution: 10,000 × 1.2 × 18 / 3600 = 60 kW.

Step 2 – With ERV (60% total efficiency).

Recovered: 60 × 0.60 = 36 kW. Net load on coil: 60 − 36 = 24 kW.

Step 3 – Coil sizing.

Coil must handle 24 kW of outdoor-air conditioning + recirculated air load. Wet-coil design with adequate drain pan.

Step 4 – Fan ESP.

Outdoor air branch ESP allowance: ERV (~150 Pa) + filter (~150 Pa final) + damper (~30 Pa) + duct (~80 Pa) = ~410 Pa on the outdoor branch.

Step 5 – Energy economic.

Without ERV: 60 kW × 4,000 equivalent full-load hrs/yr × 0.32 kW/kW = 76,800 kWh/yr. With ERV: 24 kW × 4,000 × 0.32 = 30,720 kWh/yr + ERV fan power ~ 2,500 kWh/yr → ~33,000 kWh/yr. Savings: ~44,000 kWh/yr ≈ USD 5,300/yr at USD 0.12/kWh. ERV CAPEX (incremental): ~USD 12,000 → payback ~2.3 years.

Step 6 – Replicate.

If the terminal has 4 similar outdoor-air streams, the total fresh-air load with ERV becomes 24 × 4 = 96 kW (vs 240 kW without ERV) and savings exceed USD 20,000/yr.

In a recent SongXin RFQ screening for a 4-AHU terminal expansion, the engineering team showed that adding ERVs reduced the central chiller plant sizing by ~140 kW, cutting upstream chiller CAPEX more than the ERV cost.

Filtration should be selected with pressure allowance and service access. A better filter without fan margin reduces airflow after loading.

The mechanism is pressure balance. Air moves from higher pressure to lower pressure. If exhaust or supply airflow drifts, odors, dust and unconditioned air move across zones instead of staying within intended areas.

An airport ventilation RFQ should force every supplier to quote the same airflow, filtration, ERV and IAQ condition.

RFQ input list

• Zone list: departure, arrival, baggage, security, lounge, office, ATC, retail, support.
• Outdoor airflow per zone (m³/h) and ASHRAE 62.1 calculation basis.
• Indoor temperature, RH target, CO₂ target and PM2.5 target.
• Occupancy profile (peak / average / off-hour).
• Outdoor design dry-bulb, wet-bulb or enthalpy basis.
• Filtration class (prefilter + main + HEPA if any).
• ERV type and efficiency requirement.
• AHU airflow, ESP, coil duty, drain.
• Pressure relationship for adjacent zones (ΔP per zone).
• Special operating modes (pandemic / sandstorm / smoke).
• BMS points, alarms, filter DP, CO₂ sensors, occupancy sensors.

Specification checklist

If the terminal ventilation design is early-stage, send zone loads, occupancy and fresh-air assumptions to SongXin for engineering support. The team can coordinate AHUs, ERVs, chillers and DX support units before procurement freezes the equipment schedule.

The first mistake is adding outdoor air without cooling capacity. The worked example shows that 10,000 m³/h of outdoor air with an 18 kJ/kg enthalpy difference adds 60 kW of cooling load (24 kW with ERV).

The second mistake is selecting filters without final pressure. A clean filter has lower resistance than a loaded filter, so airflow falls when the fan is not selected for final pressure.

The third mistake is mixing zones with different pressure needs. Baggage, restroom, retail, ATC and passenger halls should not all be treated as one pressure zone.

The fourth mistake is hiding AHUs behind poor access. Airport ventilation quality depends on filter changes, coil cleaning, ERV maintenance and drain service.

The fifth mistake is omitting ERV / energy recovery. With airport outdoor-air rates of 10,000–100,000 m³/h per AHU and 8,760 hours/yr operation, payback is typically 2–4 years even at low electricity prices.

The sixth mistake is not designing for special modes. Post-COVID and post-sandstorm-incident airports must switch between energy-saving (recirculation) and IAQ-priority (100% outdoor + max filter) modes – this requires AHU damper and control design from day one.

The seventh mistake is using only return-air CO₂ sensors. Demand-controlled ventilation needs zone-level CO₂ in high-occupancy areas; a single return-air sensor averages out and under-ventilates peak zones.