Fume & Dust Extraction

Ventilation & Dilution of Hydrogen Leaks with Exhaust Fans


Hydrogen is a colourless, odourless, and tasteless gas, therefore small gaseous leaks are difficult to detect by human senses. Small leaks are common due to the small size of hydrogen molecules and usually do not present a problem since the tiny amount of mixture will not be enough to cause a flammable mixture in the air. Small amounts of leaking hydrogen will rise and diffuse quickly in air because of its low density resulting in high buoyancy (it’s 14 times less dense than air).

Hydrogen is less likely to cause a fire or explosion hazard in an open or well-ventilated space, but a problem arises when hydrogen gas is allowed to accumulate in a confined area. If this is allowed to happen, there will be a risk of a flammable mixture building up. When a large amount of accumulated hydrogen rises and mixes readily with air, it creates an ignitable mixture that can result in flames or explosions. Hydrogen is flammable in air at a volume of 4-75% by volume. 

Any structure that contains hydrogen components should be ventilated adequately. Since hydrogen is lighter than air, it collects under roofs and overhangs. Most people are familiar with protecting plants from heavier than air vapours, but are unfamiliar with upward issues. There have been many reports of hydrogen leaks igniting over the decades, and several potential ignition prevention mechanisms and hydrogen leak detection systems have been proposed. 

Methods for hydrogen leak detection include:

listening for high pressure gas leaking such as a loud hissing sound
using portable hydrogen detectors 
using permanently installed hydrogen detectors linked to local facility-wise audible or visible alarms. Set at 1% by volume (25% of LFL)
monitoring piping pressures or flow rate changes
locating detectors where leaking hydrogen can accumulate
ventilation, dilution, and exhaust

Reducing the Volumetric ratio of Hydrogen to Air

Ignition can occur at a volumetric ratio of hydrogen to air as low as 4% due to the oxygen in the air and the simplicity and chemical properties of the reaction. 

The best practice to avoid accumulation is to determine where hydrogen leaks are likely to occur and how they may disperse and ventilate accordingly to manage the airflows sufficiently to keep hydrogen concentrations below the lower flammability level(LFL) during probable release scenarios. Ventilation rates should be sufficient to dilute hydrogen leaks to less than 25% of the LFL which is about 1% volume by air. The minimum ventilation rate should safely dilute hydrogen build-up in the event of leakage and the ventilation should not shut down in emergency or during periods of shut down. 

It is generally safe to exhaust hydrogen into open atmosphere providing it is kept high enough that the heat does not harm anyone. Ventilation systems should not be used for the disposal of hydrogen; this should be managed by a separate system called a vent system. 

IIC Fans for Potentially Explosive Environments

Hydrogen is a gas group IIC gas and belongs to the T1 temperature class making it one of the hottest, most dangerous gases. Mechanical exhaust fans should be ATEX rated to the appropriate IIB+H2 or IIC T1 ATEX certification andconstructed from the suitable permissible material pairings as noted in the current legislation surrounding equipment for explosive environments. Material pairings should specifically relate to the rotating and stationary parts that may come into contact with each other during standard or rare malfunction. This material pairing reduces the risk of ignition created from friction and the build up of static electricity to create a spark. ATEX fans are therefore often referred to as having a spark proof construction. 

Our entire range of ATEX certified fans are suitable for gas group IIC or IIB + Hydrogen applications for effective hydrogen ventilation. Learn more by visiting our website. 


Reducing Mechanical Sparks & Friction Explosions with ATEX Fans

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Mechanical sparks and friction are one of the most common causes of ignition of flammable gases and dust clouds. Accident statistics in Germany indicate that mechanical sparks and friction as an ignition source occurred in 32.7% of incidents.

Incorrectly selected, or fans deemed unsuitable for hazardous areas, can produce an effective ignition source caused by various incidents; hot surfaces, by mechanically generated sparks because of friction, impact, or abrasion processes (because of contact between the rotor – the rotating part, and fixed components) or by the electric discharge of static electricity when using non-conductive materials.

In the normal operation, or in the event of malfunctions (whether standard or rare), possible friction caused by areas meeting one another can occur. As stated in the ATEX directive and adopted into UK legislation, potential areas of contact between the rotating elements and fixed components of equipment for use in potentially explosive environments, should be manufactured from materials in which the risk of ignition caused by friction and friction impact sparks, hot spots or hot surfaces is minimised. This applies specifically to the construction and manufacture of explosion proof industrial fans. Ignition risks cannot be completely eliminated but can be significantly reduced by taking suitable constructive measures for avoiding ignition sources.  

European and UK Directives are clear on the permissible material pairings that are suitable to reduce the ignition source caused by friction of rotating and fixed component parts. Material pairings are considered carefully by fan manufacturers and authorised bodies. They use their theoretical and practical knowledge, coupled with the known application conditions for the environment in question, the safest material pairing and other compulsory technical specifications to determine how a product is chosen for an explosive environment.

Material pairings are devised and communicated in legislationdocumentation to minimise the risk of an explosion. Industrial fans in systems or machinery, are generally not supervised continuously and contact between rotating and stationary orfixed components, may occur in a particular area for an unknown amount of time, potentially in long intervals. 

Metal to Metal Ignition

Metal to metal ignition is caused either by rubbing friction, as mentioned earlier, such as between a rotating impeller and a stationary piece of metal, or by impact of two metal objects. Research has shown that in metal-to-metal contact, the properties of the more readily oxidised metal, normally determine the degree of ignition hazard. The hardness, melting point, ignition temperature, specific heat conductivity and brittleness of the metals all play a role, in that they determine the size, duration, temperature and heat capacity of the incendive sparks. 

An important precondition for all the protection principles is that parts which are in unhindered contact with the explosive atmosphere must not be able to reach non-permitted high temperatures with respect to the ignition temperature of substances present in the site of installation. This means that the ignition temperature is relevant for all protection principles. We cover temperature classes and surface temperature on our website.

The standard EN14986 dictates minimum design rules that industrial fans for hazardous areas should comply with. In relation to the material pairings that we introduced earlier, the below briefly seeks to improve your knowledge of the parts of ATEX fans that indicate the rotating and stationary parts that must be manufactured from these permissible materials to reduce the risk of sparks and hot spots due to frictional rubbing in the event of movement between the two parts. For more information on a wide range of ATEX topics please visit our website.

ATEX Axial Fans 

In axial fans the two parts are:

Rotating: Impeller, tip of the blades.

Stationary: The fan casing & ring

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This article can also be found in the Jan/Feb isuse.



Nederman Product Catalogue 2009/2010

Based in Helsingborg, Sweden, Nederman is a global player in working environment products and systems. Over 60 years of experience have helped the Group develop a modern and extensive product range.

Nederman is a world leader in dust and smoke extraction, exhaust fume extraction, hose and cable reels and workplace partitioning.
With sales in more than 50 countries and its own distribution network, Nederman is the best-known brand in the industry on a global basis.

The October edition of EMS magazine

ems front cover oct 09
The October edition of EMS magazine is now available to read online in page turning digital format or PDF format. This edition contains articles on achieving best practice in condition monitoring and plant maintenance as well as the latest products, news and case studies.

Explosion Proof Mobile Dust Extractor Unit

http://www.hazeng.co.uk/images/ARC%20Explosion%20Proof%20Mobile%20dustextractor.jpgWe introduce our 'unique' Explosion Proof Mobile Dust Extraction unit which is 'LEGALLY' certified ATEX Zone 21 and Zone 1 (Gas/Dust). Constructed in Stainless Steel (other materials available), it is the only Mobile unit available with this certification. Ideal for Pharmaceutical/Medical, Food industries as it has full HEPA filtration and is cleanroom compatible.

Suitable with:

•    3 metre long 304 grade S/S dust extraction arm
•    2500m3/hr centrifugal fan with 1.5kw EExd II B T5 Motor
•    9m2 multi pocket, anti static, polyester needlefelt bag filter
•    Automatic filter cleaning by timed shaker with 0.55kw EExd II B T5 Motor
•    Secondary HEPA filtration
•    Dust collection bin
•    Electrical control panel requireing 415v 3ph supply
•    304 grade S/S construction

Explosion and dust ignition proof vacuum cleaner systems

http://www.hazeng.co.uk/images/ARC%20pic.jpgARC Technologies, is the authorised distributor for ‘Tiger-Vac’ ATEX rated Industrial Vacuum Cleaner Systems for wet or dry recovery. ’ LEGALLY’ Certified for hazardous locations:  Fuel, metal dust, pharmaceutical powder, shooting ranges, flour mills, carbon black, nuclear, etc.

These vacuum cleaner systems are certified for explosion proof / ignition proof hazardous locations by an independent lab and can be used to vacuum up flammable and explosive materials. Qualified for categories 1, 2, & 3 as defined in the ATEX directive 94 / 9 /EC.

DC 1800 EX

The DC 1800 EX is suitable for general cleaning and source extraction. The DC 1800 is small and lightweight, therefore suitable for those that need a highly portable machine that still is powerful enough for source extraction. With its low weight it is easy to carry onto the job site and it can be easily stored or rolled under a workbench.

The DC 1800 is equipped with a steel container and a plastic bag can be used inside the container. It is equipped with a brushless motor (for spark-free operation) and is certified to IP5X standard.

Hazardous Area Equipment Protects Workers from Harmful Dust

Dust BoothA range of hazardous area equipment, including fluorescent emergency lighting units, stop-start pushbut-tons, connectors and terminal boxes manufactured by Cooper Crouse-Hinds, is being used on dust containment booths destined for the pharmaceuticals, chemicals and biotech markets.

Based in Huddersfield, Extract Technology designs and manufactures a range of

Thermo Fisher Scientific Introduces the Thermo Scientific Model 60i Full-Extractive,Multi-Gas Analyz

Thermo Scientific Model 60iThermo Fisher Scientific Inc., the world leader in serving science, today announced the new Thermo Scientific Model 60i, a full-extractive, multi-gas analyzer that features non-dispersive infrared (NDIR) optical filter technology to ensure accurate, precise measurement of up to six gases, including CO, CO2, NO, NO2, and SO2. The Model 60i also accommodates an optional O2 measurement capability using either an affordable electrochemical cell or, when high accuracy and reliability are required, paramagnetic technology. In addition, the unit is designed with built-in safeguards that protect the analyzer in the event of a sample conditioning system malfunction.

The high sensitivity of the Model 60i requires as little as one quarter the flow rate of other instruments, exposing the analyzer and sample conditioning system to less particulate and water for more dependable operation. The Model 60i also possesses a wider dynamic range than other multi-gas analyzers, requiring less configuration.