Description

Product Overview

A PP back draft damper is an injection-moulded polypropylene one-way valve fitted into a PP duct run. It opens with forward airflow and closes when airflow stops, so air, fumes and odours cannot move back into the duct, and it matches the round PP duct range from φ110mm to φ600mm.

The damper is injection moulded in PP or flame retardant PPs, in beige or grey, and joins the duct run by hot air welding, with socket connection reinforcement at the joint. Standard sizes cover φ110mm to φ600mm, and custom sizes are made to order. For the straight duct this damper is fitted into, see Polypropylene Round Ducts.

A back draft damper is one part of a ventilation system: it controls flow direction in the run rather than connecting or branching it, and matching fittings are available from the same supplier so a complete PP duct line can be specified from one source.

Product Selection Summary

Good Fit

• Duct runs that must not allow backflow when the fan is off
• Exhaust lines where fumes or odours could return into the space
• Outlet protection combined with a rain cap or wall terminal
• Projects needing flame retardant fittings for part or all of a run

Conditions To Confirm

• Duct diameter (φ110mm to φ600mm, 11 standard sizes or custom) and quantity
• Material grade: PP or flame retardant PPs
• The intended airflow direction through the damper
• Gas composition, concentration, temperature and moisture at the operating point

Not a Replacement For

• Fans, airflow balancing devices, rain caps, motorised control dampers or gas treatment equipment

Technical Specifications

Confirmed Product Parameters

Parameter	Value
Product Type	PP Back Draft Damper (backdraft damper for duct)
Material	PP (polypropylene) or PPs flame retardant grade
Size Range	φ110-600mm – 11 standard sizes or Customized
Connection	Hot air weld; socket connection reinforcement
Fabrication	Injection molding
Color	Beige / Grey
Working Temperature	-15℃ to 80℃
Chemical Resistance	pH 1-14 (acid and alkali)
Certification	ISO9001, ISO14001, RoHS

Available Sizes (φ)

Diameter	Diameter
φ110mm	φ355mm
φ160mm	φ400mm
φ200mm	φ450mm
φ250mm	φ500mm
φ315mm	φ550mm
	φ600mm

For sizes outside the standard range, custom dampers are made to order – confirm the required diameter with the project.

Material & Performance

Because round fittings are injection moulded rather than welded from sheet, the damper keeps the same corrosion resistance as the welded duct while offering consistent moulded dimensions, smooth surfaces and a shorter production time for standard sizes.

PP back draft dampers are injection moulded from polypropylene, chosen for corrosive fume handling in ductwork:

• Acid and alkali resistance: PP withstands corrosion by high-concentration acids and alkalis across a wide pH range (pH 1-14).
• Sound insulation: PP reduces vibration and noise transmitted through the fitting.
• Light weight: moulded PP fittings are light and easy to handle and weld on site.
• Consistent moulded dimensions: each size is produced to a standard mould, giving uniform dimensions and wall thickness across batches.
• Long service life: PP duct systems offer a service life of up to 50 years under specified operating conditions.
• Anti-condensation: PP conducts heat poorly, reducing condensation and heat loss at the fitting.

Flame retardant PPs is available where fire-rated ductwork is required; specify the required flame retardant grade when inquiring. The material grade applies to the whole fitting, so a single grade can be specified across the duct, fittings and accessories in the run.

Applications

One-Way Flow Control

Back draft dampers are fitted at the points in a duct run where airflow must move in one direction only:

• After the fan – preventing air moving back through the fan when it is off
• Before the outlet – stopping fumes and odours returning into the building through the exhaust
• On branch lines – isolating a branch so air does not flow back from the main line
• At outdoor terminals – combined with a rain cap to keep backflow and weather out of the duct

With forward airflow the damper opens and the run flows freely; when the fan stops or pressure reverses, the damper closes and seals the run. This is automatic – no actuator or operator is needed for the one-way function.

Selection Notes & Quotation Information

Back Draft Damper or Control Damper?

A back draft damper is an automatic one-way valve: it opens and closes by itself to stop backflow. A control damper – such as an electric damper valve or manual air damper valve – regulates airflow volume by adjusting the opening. Use a back draft damper where backflow protection is the need; use a control damper where airflow must be adjusted or shut off.

To Quote PP Back Draft Damper

Provide: duct diameter (φ110-600mm or custom), quantity, material grade (PP or flame retardant PPs), color (beige or grey), airflow direction, application, destination port, and your duct schedule or drawings.

MOQ and lead time are confirmed per project. Request a quote via WhatsApp or email using the contact block below.

Installation & System Integration

PP back draft dampers are joined to the duct run by hot air welding, and the joint is reinforced with a socket connection. The damper is installed in the direction of intended airflow, so the flow direction is confirmed before fitting. The same joining method applies to straight duct and other fittings, so the damper becomes part of one welded, sealed system.

Complete systems combine back draft dampers with straight duct, rain caps, elbows and couplings. See the full range of PP duct systems.

Related Products

• Polypropylene Round Ducts
• PP Duct Rain Cap
• Electric Air Damper Valve
• Manual Air Damper Valve
• PP 90° Elbow
• Full PP Duct Range
• PP Air Duct Guide – a complete guide to PP duct types, sizes and materials.

FAQ

What is a PP back draft damper?

It is an injection-moulded polypropylene one-way valve fitted into a PP duct run – it opens with forward airflow and closes when airflow stops, so air, fumes and odours cannot move back into the duct.

How does it work?

With forward airflow the damper opens and the run flows freely; when the fan stops or pressure reverses, the damper closes and seals the run. The one-way function is automatic, with no actuator or operator.

What sizes are available?

11 standard sizes from φ110mm to φ600mm: φ110, φ160, φ200, φ250, φ315, φ355, φ400, φ450, φ500, φ550 and φ600mm – plus custom sizes made to order.

Back draft damper or control damper – which should I choose?

A back draft damper is an automatic one-way valve for backflow protection. A control damper – electric or manual – regulates airflow volume by adjusting the opening. Use each where its function is needed.

Is flame retardant PP available?

Yes. The damper is available in standard PP or flame retardant PPs; specify the required flame retardant grade when inquiring.

What do I need to provide for a quote?

Duct diameter, quantity, material grade, color, airflow direction, application, destination port, and your duct schedule or drawings.