Jet Fan for Underground Car Parks: A Complete Guide for Designers and Investors

Everything you need to know about impulse ventilation fans for car parks — from operating principles and mandatory regulations to choosing the right model

Why Underground Car Park Ventilation Is More Complex Than It Appears

An underground car park is not simply a space where people leave their cars. It is an enclosed environment with no effective natural ventilation, in which dozens or hundreds of combustion engines daily emit carbon monoxide, nitrogen dioxide and unburned hydrocarbons. In case of fire, the same space can become an unbreathable environment within minutes, with temperatures of hundreds of degrees Celsius and dense smoke blocking evacuation routes.

Designing a ventilation system for an underground car park is therefore not a minor technical detail. It is a legal obligation, a condition for obtaining the operating permit, and above all a measure that can save lives.

The most modern and efficient solution for underground car park ventilation and smoke extraction is the impulse ventilation system — Jet Fan. This guide explains in detail what they are, how they work, what regulations apply in Romania and what models are available on ventilation.ro.

What Is a Jet Fan and How Does It Work

A Jet Fan (impulse ventilator) is a piece of equipment mounted at ceiling level in the car park that generates a powerful, directed airstream without using traditional ductwork. Unlike classic systems with channels and extraction grilles, Jet Fans operate on the induction principle: the high-velocity jet of air expelled by the fan entrains a significantly larger volume of ambient air from the adjacent zone (Coandă effect), thereby creating an organised flow throughout the entire car park.

This directed flow transports pollutants (CO, NOx) or fire smoke from the source to strategically positioned exhaust outlets at the ends of the car park, where large-volume axial fans extract it definitively to the outside.

Advantages over traditional duct systems:

The Jet Fan system completely eliminates the need for a complex and expensive distribution ductwork system with grilles, fire dampers and regulating dampers. Impulse fans eliminate the need for investment in costly air distribution systems, dampers or fire shutters, also reducing maintenance costs. Installation cost is significantly lower, especially in large or geometrically complex car parks, and subsequent maintenance is considerably simpler.

Correct project management across all development phases requires the use of computational fluid dynamics — CFD simulation — which provides a guarantee of efficient system operation. This means that before installation, the designer can virtually simulate the behaviour of air and smoke in the actual car park space, validating the number and position of Jet Fans.

The Two Functions of a Jet Fan: Normal Ventilation and Smoke Extraction

A modern Jet Fan simultaneously fulfils two distinct roles, corresponding to two operating modes:

S1 Mode — Normal ventilation (continuous operation): The system operates permanently at normal speed, extracting carbon monoxide emitted by combustion engines and maintaining CO concentration below permitted limits (generally below 50 ppm, per STAS 12574). Activation can be automatic, through CO sensors integrated in the car park management centre.

S2 Mode — Smoke extraction in case of fire (emergency operation): At the fire panel signal, the system switches to maximum speed and, in the case of reversible models, can also change the flow direction to optimise smoke extraction. The impulse fans direct smoke towards the extraction outlets, where fire-rated fans (class F400/120) extract it to the outside. In this mode, the air temperature can reach 300°C or 400°C for 2 hours without the fan deteriorating.

Mandatory Regulations in Romania

Any ventilation system for an underground car park in Romania must comply with a clear regulatory framework:

What NP 127:2009 provides regarding Jet Fans:

Mechanical smoke extraction installations shall be provided with automatic activation in case of fire and manual controls located near entrances and in security control rooms.

Smoke extraction fans in case of fire must be fire-rated, class F400/120. Smoke-directing Jet Fans (mounted inside the car park) must be class F300/120, in accordance with EN 12101-3.

Smoke extraction openings shall be mounted at the upper part of the space being smoke-extracted, in the upper third of walls or in the slab, connected directly or through ductwork to fire-rated fans.

Types of Jet Fan: Axial vs. Centrifugal (with Induction)

From a constructional point of view, Jet Fans available on ventilation.ro are divided into two main categories:

1. Axial Jet Fan (with impulse) — JF series

The axial impulse fan is the classic construction for car parks with sufficient clear height (minimum 2.2–2.5 m to ceiling). It generates a linear high-velocity air jet with an effective range of 15–25 metres depending on the model.

Distinctive features:

• Circular or octagonal (low profile) construction
• Ceiling mounting, suspended on brackets or consoles
• Available in unidirectional or reversible variants
• Asynchronous three-phase motor 400V/50Hz, IP55, Class H
• CE certification per EN 12101-3, classes F300/120 and F400/120

On ventilation.ro — Axial JET fan — JF series (UN CONFORT):

The JF 300 T2/T4 series available on ventilation.ro consists of an axial fan flanked by two sound attenuators. JF models consist of an axial fan and two attenuators. The casing is zinc-coated steel, with an interior duct of perforated zinc-coated steel sheet. The sound attenuators are filled with mineral wool with high sound absorption properties, preventing propagation of most fan noise.

Indicative price: ~17,621 RON incl. VAT for the JF 300 T2/T4 model.

2. Centrifugal Jet Fan (with induction) — CI / Centrifugal JET series

The centrifugal induction (or impulse) fan is the preferred solution for car parks with limited clear height or where the space geometry does not permit standard axial Jet Fan mounting. Due to its compact form and reduced profile, it can be installed in spaces with a clear height of as little as 1.8–2 m.

Features:

• Ultra-low profile (Low Profile) — ideal for low-headroom basements
• Backward-curved blade rotor, zinc-coated steel
• IP55 motor, Class H, continuous S1 and emergency S2 operation
• F300/120 and F400/120 certified per EN 12101-3

On ventilation.ro — "Centrifugal JET impulse" category:

ventilation.ro offers a complete range of centrifugal JET impulse fans, included in the "Smoke extraction in case of fire" category, with indicative prices from ~3,368 RON to over 24,000 RON depending on power and certification.

Architecture of a Complete Jet Fan Ventilation System for an Underground Car Park

1. Impulse Jet Fans — mounted on the ceiling, at CFD-calculated spacings, oriented to create an organised airflow from the air inlets to the extraction outlets.

2. Fire-rated extraction fans (F400/120) — mounted at the ends of the car park or in technical shafts, providing final extraction of polluted air or smoke to the outside.

3. CO sensors and smoke detectors — integrated in the management centre, automatically switching the system from S1 (normal ventilation) to S2 (emergency smoke extraction) mode.

4. Fire panel and UCMS — the Manual Centralised Security Command Unit, mandatory per NP 127:2009, allows operators to manually activate the smoke extraction system.

5. Air supply — the access ramp, lateral openings or fresh air supply fans provide the make-up air necessary for the extraction system operation.

6. CFD study — not an optional accessory, but a mandatory component of the project. The system performance is verified through CFD simulation, confirming that in the event of a fire, smoke evacuation will be achieved correctly.

How a Jet Fan System Is Sized: Essential Parameters

Normal ventilation airflow (CO): Calculated based on the number of parking spaces, traffic type, car park surface area and volume.

Car park classification: Per NP 24-2022, car parks are classified as open, closed and underground, each category with specific ventilation requirements. Underground car parks require mandatory artificial ventilation.

Number and positioning of Jet Fans: Established through CFD simulation, accounting for the space geometry, structural columns, clear height, access ramp position and extraction outlet positions.

Fire resistance class: Smoke-directing Jet Fans inside the car park must be minimum F300/120, and final extraction fans minimum F400/120.

Individual Jet Fan parameters:

• Thrust force (N) — how many newtons of force the air jet generates
• Self-airflow (m³/s) — volume of air directly expelled
• Effective range (m) — distance at which the jet remains effective
• Noise level (dB(A)) — relevant for car parks adjacent to occupied spaces

Products Available on ventilation.ro for Underground Car Parks

ventilation.ro holds over 130 products in the Underground Car Parks category, including:

Axial impulse Jet Fans — the "JET impulse" category includes axial impulse fans with integrated sound attenuators, certified for fire operation. The JF series (UN CONFORT) is available in multiple power configurations (T2 and T4), with indicative prices from ~17,000 RON for basic models.

Centrifugal JET impulse fans — the "Centrifugal JET impulse" category covers low-profile ranges ideal for car parks with limited clear height. Prices start from ~3,368 RON for smaller models.

Fire smoke extraction fans (F400/120) — the "Smoke extraction in case of fire" range on ventilation.ro comprises over 430 products — axial, rooftop and centrifugal fire-rated fans completing the Jet Fan system as final extraction fans.

Comparison: Jet Fan System vs. Traditional Duct System

Frequently Asked Questions from Designers and Investors

Q: Is a CFD study mandatory for every underground car park? A: Yes, for car parks with a Jet Fan system, the CFD study is practically mandatory at the project stage, as it is the only way to demonstrate that the system will operate per regulations.

Q: Can Jet Fans be used in car parks with electric vehicles? A: Yes. Car parks with electric vehicles present specific risks related to lithium-ion batteries. Jet Fan systems are adaptable for these scenarios; the project must account for specific risks and any additional requirements from NP 24-2022.

Q: How long does installation of a Jet Fan system take compared to a traditional one? A: A Jet Fan system is generally installed 30–50% faster than a duct system, as distribution channel assembly is eliminated.

Q: Can Jet Fans be integrated with the building BMS? A: Yes. Fans available on ventilation.ro are compatible with management centres and can be controlled via 0–10V signals or digital protocols.

Conclusion

Underground car parks in modern residential developments, shopping centres, hotels and office buildings being built today in Romania have a single viable solution for ventilation and smoke extraction: the Jet Fan impulse system.

ventilation.ro provides designers and investors with a complete range of fans for underground car parks — from axial and centrifugal Jet Fans certified F300/120 and F400/120, to final extraction fans and CO sensors for BMS integration.

Browse the complete range on ventilation.ro or contact the team of specialists at +40 722 667 239 for technical advice and a personalised offer for your project.