BVNC 40 — Overpressure Blast Valve for Protective Shelters

Oct 18

4 min read

Introduction

The BVNC 40 Overpressure Blast Valve is a normally closed valve designed to maintain and control differential pressure levels inside a shelter while protecting the internal space against external blast-wave pressure.

According to the product description, the valve operates automatically. When positive pressure inside the shelter reaches a predefined overpressure level, the valve releases air from the protected space. This function supports controlled air release and pressure regulation in shelter ventilation systems. Atmas Group

The BVNC series was developed for use in civil defence shelters, bunkers, safe rooms and other protected spaces. The product range includes valves designed for different airflow requirements. Atmas Group

Official product page: BVNC 40 — Overpressure Blast Valve

Operating Principle

The BVNC 40 is a normally closed, automatic-action overpressure valve.

Its specified operating principle consists of two main functions:

Pressure control: the valve helps maintain and control differential pressure levels inside the shelter.
Automatic air release: when positive pressure reaches the predefined level, the valve releases air from the shelter.

The valve is designed to provide controlled air release while protecting the internal space from external blast-wave pressure. Atmas Group

This operating principle makes the BVNC series relevant to ventilation arrangements in which maintaining a controlled internal pressure and managing air exhaust are important design requirements.

Applications in Shelters and Protected Spaces

The manufacturer identifies the following applications for BVNC overpressure valves:

Civil defence shelters
Bunkers
Safe rooms
Other protected spaces

The valves are designed for installation in ventilation openings or as part of an air duct. The BVNC product family includes different models to accommodate different airflow requirements. Atmas Group

For more information about related ventilation equipment, see the Atmas Group blast and overpressure valve catalogue.

Protection Against External Blast Pressure

The BVNC 40 is designed to protect the shelter's internal space against external blast-wave pressure.

Its published operational reflected blast pressure durability exceeds 900 kPa. This is the operational pressure-durability figure stated in the product specifications. Atmas Group

This parameter should be distinguished from the valve's airflow and pressure-drop specifications. It describes a separate aspect of the product's stated performance.

Automatic Overpressure Regulation

The BVNC 40 is designed to release air when the positive pressure inside the shelter rises to the predefined level.

According to the product description, this automatic operation supports control of differential pressure inside the protected space. The valve is normally closed and opens to release air when the required overpressure threshold is reached. Atmas Group

The specific pressure threshold for activation is not stated in the supplied product information and is therefore not specified in this article.

Installation and Construction Characteristics

The BVNC 40 is designed for installation on ventilation openings or as part of an air duct. Its specified standard flange size is 4 inches. Atmas Group

The product description also states that BVNC valves are designed to operate across a wide range of temperatures and are resistant to corrosion. These characteristics are identified by the manufacturer as features of the product family. Atmas Group

The suitability of a particular installation should be assessed against the requirements of the ventilation system and the specified connection configuration.

Main Technical Specifications

Parameter	BVNC 40 specification
Product type	Overpressure blast valve
Valve operation	Normally closed, automatic action
Operational reflected blast pressure durability	>900 kPa
Nominal airflow	40 m³/h
Pressure drop at nominal airflow	200 Pa
Mechanical shock resistance	>12 g
Standard flange	4 inches
Installation	Ventilation opening or air duct

The specifications above are taken from the published BVNC 40 product information. Atmas Group

BVNC 40 Within a Shelter Ventilation System

The BVNC 40 is one model in the BVNC family of overpressure blast valves. The series includes other models with different nominal airflow ratings, allowing the valve selection to be matched to the airflow requirements of the intended application. Atmas Group

When selecting a valve, the principal published parameters to consider include:

Nominal airflow
Pressure drop at nominal airflow
Operational reflected blast pressure durability
Mechanical shock resistance
Flange size
Installation arrangement

These specifications provide a basis for evaluating the product in the context of the complete shelter ventilation system.

For related products and technical information, consult the official resources below.

Conclusion

The BVNC 40 Overpressure Blast Valve is a normally closed, automatic-action valve designed to control positive pressure and release air from shelters when the predefined overpressure level is reached.

Its published technical specifications include a nominal airflow of 40 m³/h, a pressure drop of 200 Pa, operational reflected blast pressure durability exceeding 900 kPa, mechanical shock resistance exceeding 12 g, and a standard 4-inch flange. Atmas Group

The valve is designed for civil defence shelters, bunkers, safe rooms and other protected spaces, with installation on ventilation openings or within air ducts.

For full product details and purchasing information, visit Shelter Shop.