Industrial Products

Vent Silencers


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Vent silencers, blow-off silencers, and blowdown silencers are interchangeable terms for devices that attenuate the noise generated by the sudden release of high-pressure gas.

Common to most high pressure gas or steam applications is the need to vent or evacuate a system in the event of an upset or system shut down.  As a result, relief valves and/or control valves are incorporated to safeguard against a system failure or maintain process conditions.   VAW’s steam vent and blow-off silencers are specially designed to reduce noise generated by the high differential pressure at the time of a release.   Each silencer is designed for the individual process venting conditions and customer acoustic requirements.  Materials selection is based on the application criteria as it relates to the vented medium (steam, air, natural gas, or other gas), upstream pressure and temperature and flowrate required to be vented. VAW’s Applications engineering team have the knowledge and experience to correctly design the proper vent silencer for your system.



The specifications of our vent silencers vary depending on the level of noise reduction that must be achieved, the type of vent, the kind of gas, its flow rate, and many other factors. Our team constructs custom-built vent silencers with different shapes, sound-absorbing materials, and other features depending on these and other factors.

Types of Vent Silencers

Standard Vent and Blow-Off Silencers

The standard design for a vent silencer typically consists of a heavy duty inlet flange that lets the gas enter the silencer, an expansion chamber that allows the gas to expand, reducing its pressure and velocity, and a permeable area with sound-absorbing material. The silencer’s outside diameter and length will vary based on performance requirements and site installation conditions.   

Hooded Vent and Blow-Off Silencers

These silencers have the same basic design as standard silencers but with a hood over the outlet to direct sound. Typically, the sound is aimed upward to reduce ground-level noise

Silencer Sizing/Selection

Various factors are considered when selecting the size, material, and other features used in a vent silencer, including:

  • Gas type (steam, natural gas, or other)
  • Temperature upstream of the valve
  • Pressure upstream of the valve
  • Service (Intermittent venting or continuous venting)
  • Unsilenced noise level
  • Required silenced noise level (dBA)
  • Distance from outlet
  • Receiver angle relative to outlet (typically 90-degrees)
  • Silencer shell materials
  • Flange connection size
  • Flange connection rating
  • And more

We will work with you to select the right size, shape, and construction for your vent silencers. 

Design and Installation

VAW Systems can handle every design, engineering, and installation element on your behalf. We even have our own research facility, allowing us to develop completely novel noise reduction technologies when needed.


  • Steam safety relief valve outlets
  • Process steam control valves
  • Steam ejectors
  • Compressor by-pass valves
  • Boiler start-up and steam purge systems
  • Steam and gas vents
  • Switch valves (reversing valves)
  • Autoclaves
  • By-pass valves

Standard Features

  • Single or multiple inlets
  • Compact single or multi-stage diffusers
  • All welded, heavy-duty construction
  • Materials: Painted carbon steel
  • Paint finish
  • Flanged, NPT or BFW connections
  • Vertical and Horizontal mounting brackets
  • Condensate drains

Construction Options

  • Materials: Stainless steel
  • Special paint and corrosion resistance systems
  • Support Brackets as required
  • Weather hoods
  • Outlet elbows
  • Bird screen

Why Choose VAW Systems?

With our own research facility, ISO 9001:2008 certification, and over 40 years of experience in the industry, VAW Systems is the leading innovator in noise control and noise reduction products for commercial and industrial use. Having innovated everything from new parts to sophisticated selection technology powering the noise reduction industry, we will find the perfect noise control solution for your needs. 

Contact Us

Stay in line with local noise level by-laws and keep your machinery running better for longer. Contact VAW Systems for vent and blow-down silencers.


What Is the Difference Between Steam Vent Silencers and Blow-Off Silencers?

The terms steam vent silencer and blow-off silencer are often used interchangeably. They are silencers that are used to reduce the noise created by the sudden release of high-velocity gas. Steam vent silencers are specifically used for steam vents, while the term blow-off silencer could technically be used for any release of high-velocity gas. 

Why Are Vent Silencers Necessary in Industrial Applications?

When large volumes of high-pressure air or gas are released all at once, it can create noise exceeding 120 decibels. These loud noises can violate noise pollution by-laws and can damage the hearing of workers at the facility. Additionally, noise can create vibrations that speed up the wear and tear on boilers and other high-pressure systems. Vent silencers will significantly reduce the amount of noise generated.

Can VAW Systems' Silencers Be Customized?

Yes, we customize solutions for virtually any vent configuration and space constraint. Your vent silencer will be custom-engineered and manufactured to suit your exact needs. 

How Do I Know Which Silencer Is Right for My System?

Knowing which vent silencer suits your system installation and noise emissions criteria can be difficult. Talk to the experts at VAW Systems; we’ll get your information and design the vent silencers to suit your needs. 

What Information Do I Need To Provide for a Custom Silencer Design?

To get the ideal vent silencer for your needs, you will need to provide us with:


  • Site plans
  • Photos of the machinery and vents which need silencing (ideally for existing systems)
  • Information about the vent being silenced, including
    • Quantity of vent silencers needed
    • Gas type (steam, natural gas, or other)
    • Temperature upstream of the valve
    • Pressure upstream of the valve
    • Service (Intermittent venting or continuous venting)
    • Required silenced noise level (dBA)
    • Distance from outlet
    • Receiver angle relative to outlet
    • Silencer shell materials
    • Flange connection size
    • Flange connection rating
Are There Maintenance Requirements for These Silencers?

Our vent silencers do not require significant maintenance. However, as with any part, regular inspection and cleaning can help prolong its life.