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Frequently Asked Questions

22 years Ventilation System Experts

Your ventilation questions answered

Our Frequently Asked Questions are sorted according to the following topics:

  • Welding and fume extraction
  • Personnel cleaning
  • Air drying
  • HVAC fans and Industrial ventilation
  • Terms and conditions of sale


What does local exhaust ventilation (LEV) mean?

Local exhaust ventilation (LEV) is the term given to the “engineering system that captures dust, vapours, and fumes at their source and transports them away from the worker’s breathing zone, to prevent workers from inhaling these substances and reducing contamination of the general workplace air.” (Worksafe NZ)

It can also be referred to as at-source fume extraction or source capture ventilation. 

Experienced ventilation engineers should be consulted when installing LEV into a workplace. 

For more information about LEV, and helpful diagrams and resources, visit:

What does ATEX mean?

ATEX is an acronym (in French) for equipment intended for use in ATmospheres EXplosible derived from EU law– meaning hazardous, or potentially explosive environments both gaseous (eg petrochemical) and dusty (eg flour mills, saw mills, some food processing plants). It usually only applies to countries in the EU.

ATEX approved equipment is certified for safe use in hazardous and dust areas and is usually marked with the Ex symbol.

Hazardous Zones 1& 2 gas/vapour/mist infographic

Hazardous zones 1 & 2 – gas/vapour/mist

Dust zones 21 & 22 – dust/fibres

IECEx is the International Electrotechnical Commission Scheme for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres. It is a voluntary certification scheme, designed as a common set of safety standards, for use by manufacturers in any country around the world. IECEx is not mandatory or law - it is a set of standards (ATEX is EU law).

IEC, EICex logos designating ATEX standards apply

What is activated carbon filtration?

Carbon filtering is a method of filtering that uses a bed of activated carbon to remove contaminants and impurities.

Activated carbon is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms. Activated carbon has a large surface area available for absorption and has a capacity to absorb any vapour contaminant.

Charcoal filters are often used in air conditioning units and exhaust fans to rid air of unwanted odors (smoke, fumes, and animal odor). Typical particle sizes that can be removed by carbon filters range from 0.5 to 50 micrometres.

What does FIO/free-blowing capacity mean?

FIO is an acronym for Free Inlet and Outlet. It, and “free-blowing”, refers to a fan installation set-up where there is no ductwork or variations to the fan’s flow rate and static pressure.

Some of the Plymoth (Alfi) fans are listed as “FIO” and others as “Do not run FIO”. This refers to whether discharge (outlet) ductwork should be included in the installation or not.

When do you need a HEPA filter?

HEPA is an acronym for a “High Efficiency Particulate Air” filter. HEPA is a standard of filtration, not a product or material - the standards require that a very high percentage (99.97%) of all particulate of a certain size (sub-micron) is trapped within a filter to provide better air quality.

The two most common HEPA standards are H13 and H14:

  • H13 – requires that the air filter must remove from the air that passes through it, 99.95% (Europe) or 99.97% (ASME) of particles that have a size greater than or equal to 0.3 sub-micron
  • H14 – requires that the air filter must remove from the air that passes through it, 99.995% of particulates greater than or equal to 0.3 sub-microns

A HEPA filter would be recommended for use in clean rooms, medical facilities, vehicles, aircraft, homes, and dusty/hazardous dusty work environments.

What does a “Jet-Pulse” self-cleaning filter mean?

The Jet-Pulse cleaning system uses compressed air for cleaning filter cartridges. Jet-Pulse cleaning is faster and more efficient than ordinary ”back-pulse” cleaning systems.

The Plymoth Jet-Pulse cleaning system includes a specially designed oscillating rubber nozzle. It oscillates under 6 Bar compressed air pressure inside the filter cartridge. It hammers the inside of the filter cartridge so that dust on the surface falls off. At the same time, it blows out the fine dust which has penetrated the surface of the filter cartridge. The result is a cartridge as clean as new after just two minutes of cleaning.

How often do we need to change the filters:

Fume extractor

  • When the filter gets dirty, the airflow volume will drop off to a level where capture of contaminates is not adequate. 
  • If your fume extractor has a Jet-Pulse self-cleaning filter, then activate it at this time. But at some point, even Jet-Pulse cleaning becomes ineffective, and this is when a filter replacement is required.
  • Contact DEA for replacement filter parts

HEPA filter

  • In general, HEPA filters should be changed every year.
  • Contact DEA for replacement filter parts

What are some options to extract fumes in remote or unusual workspaces eg closed-in environments or areas that are difficult to reach with normal smoke reduction systems?

If you are welding, cutting, grinding, gouging in a confined space, working in a large open space, working off-site, or working on a large piece of equipment (eg mining vehicles), and you are looking for at-source fume extraction options, consider the following:

  • Portable fume extractor – lightweight portable all-in-one filter suitable for low-medium level concentration of particulate, with retractable hoses and magnetic nozzle
    • AER201 portable filter unit for welding – 1.1kW motor (single phase), 250m3/h flow rate, under 72dBa noise level, 2m hose, activated carbon or HEPA filter, 18kg
    • Portaflex 200 – 1kW motor (single phase), 160m3/h flow rate, 2.5m hose, HEPA filter optional, 15kg
    • Portaflex 200 auto – 1kW motor (single phase), 160m3/h flow rate, 2.5m hose, HEPA filter optional, extraction starts/stops with welding activity, 15kg
    • Portaflex 400 – 1+1kw motor (single phase), 230m3/h flow rate, dual motors, 2.5m hose, HEPA filter optional, 15kg
  • Mobile fume extractor – trolley-mounted mobile all-in-one filter for medium-low level concentrations of particulate. Use with self-supporting articulated arms -2-3m – purchase separately.
    • UNI2.2 Mobile filter unit for welding – 1.1kW motor, 2259m3/h flow rate, <70 dBa noise level, HEPA filter
    • MF Mobile filter for welding – 0.75kW motor (single phase), 1200m3/h flow rate, activated carbon filter optional
    • MF Eco Mobile filter for welding – 0.75kW motor (single or 3 phase), 1200m3/h flow rate, comes with Jet-Pulse self-cleaning filter system, HEPA filter optional


How often do we need to change the filters:


  • Cleaning station filters (including cleaning station in standard booths) – we recommend that the filter is inspected at least once a month, and replaced after a maximum of 3 months.
  • Extractor filter (booths) - we recommend replacing the filter every 6 months
  • Contact DEA for replacement filter parts

Does a JetBlack blow more dangerous particles around in the air?

No, the JetBlack Safety Personnel Cleaning Booth removes, extracts and collects dust and debris from employees’ dirty work clothes in a containment booth, and is local exhaust ventilation (LEV) compliant (UK). Inside the booth, a high volume of filtered air is delivered at low pressure which dislodges dust and fibres from the worker’s clothes. These are then drawn down and away from the booth occupant through a grille floor, by a vacuum effect created by an external blower. All removed materials are either collected in an H14 HEPA extractor, or can be vented directly into the workplace’s existing exhaust system.

The wall-mounted and portable personnel cleaning stations are not contained within a booth, and therefore will produce airborne dust during the removal of debris and contaminants. It is recommended users wear appropriate eye, ear and respiratory protection at all times whilst operating a JetBlack Safety Cleaning Station. It is also recommended that users implement suitable and adequate engineering controls for the release for hazardous airborne dust, and consider appropriate positioning of the cleaning station prior to use/installation.


What is the difference between axial and centrifugal industrial fans?

Dynamic Engineering Australia is the Australasian distributor for Air Control Industries (ACI)'s product range. ACI has a very helpful Guide to Industrial Fans article that should answer most of your questions.

How often do we need to change the filters?

See ACI’s article: “The Importance of keeping industrial fan filters clean

Dynamic Engineering Australia (DEA) is the Australasian distributor for Air Control Industries (ACI) product range. Contact us for replacement parts.


What is an air-knife and when would you need one? 

An air knife is an industrial tool used to blow off liquid from products as they travel on conveyers - they are normally used in manufacturing. An air knife provides a high velocity curtain of air that can remove surface debris, dust, water, and any other liquids that may form or pool during the manufacturing process. Air knives can be stationary where the product passes through the air curtain (eg bottles and cans on a conveyor), or the product can be stationary and air knives move reciprocating nozzles over the surface of the product (eg crates).

Air knives are particularly useful in the food and beverage industries where cleanliness and hygiene are paramount. 


What is the warranty for your products?

Dynamic Engineering Australia’s Terms and Conditions outline our Limitations of Warranties. But in general, we will warrant for a period of twelve (12) months from the date of delivery that all goods are free from defects in material and workmanship under normal use and service, and will replace, repair or issue a credit for any parts which are returned during that period.

We can solve your ventilation challenges