FAQ air filtering technology - we answer the most frequently asked questions

Germ-free air and sterility as protection against life-threatening infections and dangerous germs is one of the basic requirements in the medical and pharmaceutical sector. Innovative air cleaning systems guarantee clean and particle-free air to protect people, products and work processes. The main areas of application are hospitals, the pharmaceutical industry, laboratories, foodstuffs production and nanotechnology.

Why do I need air filtering technology? 

  • To guarantee sterile and germ-free air
  • To reduce the risk of infection or contagion
  • To establish a stable protective zone
  • To provide a draught-free and comfortable room climate
  • To regulate room temperate

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Marchhart air filtering technology: Marchhart is an internationally operating high-tech metal processing company with focus on air cleaning systems. Highest product quality paired with innovative product features and potential benefits have top priority.
At Marchhart customers benefit from our long-standing experience as operating theatres worldwide are equipped with Marchhart air filtering technology. After a comprehensive consultation we develop a tailored concept and individually adapt the products to the respective requirements.

Your benefits from Marchhart air filtering technology: 
+ Comprehensive service portfolio – from a single source
+ Accompaniment of customer projects from concept to completion
+ State-of-the-art products, clean room concepts, air supply and extraction systems
+ Maximum casing sealing through high level of prefabrication
+ Complete solutions
+ Customised solutions
+ Expert advice and planning 
+ Long-standing expertise
+ Best matching solution addressing the needs and requirements of the customer
+ Modern machinery and equipment
+ High proportion of in-house production (high manufacturing depth)
+ Punctual delivery worldwide
+ Shorter installation times thanks to fewer complex system components
+ On-site commissioning and training

>> Marchhart air filtering technology in the medical sector
>> Marchhart air filtering technology in the pharmaceutical sector
>> Marchhart air filtering technology in the industry

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A clean room must have a particular defined air purity throughout the entire space. All materials used must also comply with specific thresholds (primarily ISO 14644-1 with the different ISO classes). This involves a wide variety of particles, dust, microorganisms or germs that have to be filtered from the air so that personnel, products and work processes remain protected.
A clean or ultra-clean room is a room in which the concentration of airborne particles is kept extremely low. Clean and ultra-clean rooms are needed for special manufacturing procedures, especially in semiconductor manufacturing where particles in ordinary air would disrupt the structuring of integrated circuits in the range of fractions of a micrometre. Clean rooms and clean room technology are also deployed in optical and laser technology, aerospace technology, life sciences and medical research and treatment, research and aseptic production of foodstuffs and pharmaceuticals as well as nanotechnology (Wikipedia).

When selecting air flow types a distinction is made between turbulent mixed ventilation and low-turbulence displacement flow. 
With turbulent dilution or mixed flow the filtered clean air is introduced into the clean room in a turbulent (swirling) manner and creates a steady dilution of the particle concentration. The required clean room class is then maintained with clean room compliant behaviour of the personnel. Special care must be taken here to minimise particle generating objects and processes in the clean room.
With low turbulence displacement flow, also referred to as laminar flow, the clean air flows into the clean room with low turbulence and usually vertically, so that the contamination of sensitive work areas and machinery is kept as low as possible. The air then escapes the room on the opposite surface, normally through the perforated raised floor, and is returned to the recirculation unit for repeated filtration (Wikipedia). 

For rooms with lower air purity requirements turbulent mixed ventilation with ceiling mounted swirl diffusers and HEPA filters are usually used, whereas laminar flow with correspondingly higher filter classes is used to satisfy higher requirements.
The right room air concept for the clean room
Drafting of an appropriate room air concept for the respective room class requires amongst others consideration of the following parameters and their fine optimal alignment:
- flow type
- air volume, air velocity 
- supply, recirculated, extraction air
- room temperature
- humidity
- noise level
Interferences such as personnel, machines, flow obstacles, heat sources or vibrations are also to be taken into account during the design phase.
Materials used in clean rooms must have abrasion-resistant surfaces. Installed systems and equipment may only minimally obstruct the laminar air flow. Components and machines that are to be brought into the clean room must be cleaned beforehand. As a rule, a clean room is under positive pressure (positive pressure ventilation). In special cases clean rooms are also operated with negative pressure, preventing for instance hazardous substances or pathogens from escaping to the outside.
Laminar flow units can also create qualified low-dust and low-particle workplaces where a purified vertical or horizontal air flow and curtains ensure that particle concentration in the air and hence particle deposits on the product are reduced.
The air conditioning processes and system types used are designed to ensure that impurities are immediately removed from the air. To this end a low-turbulence displacement flow (laminar flow) is used. Purity of the air is to be ensured through a combination of a usually multi-stage filtering and high airflow rate (Wikipedia).

Marchhart specialises primarily in the field of clean air technology in hospitals and the pharmaceutical sector, producing ventilation systems addressing individual requirements.

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The German abbreviation TAV stands for low-turbulence displacement flow which is referred to in English as laminar airflow. Therefore we often also refer to laminar air flow ceilings or LAF ceilings. LAF ceilings are mostly used in the medical sector to achieve a predefined protective zone in correspondence with the desired room class. This type of surgical ventilation ceiling is however also used in other sectors where a clean room is required. The aim is always to free the air as best as possible from dangerous germs and particles, to create a stable protective zone and to discharge the contaminated air in a particular manner.

As the name "laminar air flow” implies the air flow cleaned by filters is directed into the protective zone with low turbulence, i.e. with as little swirling as possible, thus ensuring clean air in sensitive work areas such as an operating theatre. The air in the protective zone itself is inevitably contaminated by a large number of germs or particles (e.g. by the surgical team, microorganisms and germs, bacteria…) so immediate targeted discharge by means of downward flow is absolutely indispensible. Germ-free conditions must also prevail and be ensured in the instrument prep-zones, on instrument tables or on implants. With a Marchhart LAF ceiling these aspects are also covered.

LAF ceiling with air conditioning system
If desired and reasonable the air can be cleaned again through a multi-stage filtering system and fed back to the protective zone using a recirculation system. This makes sense especially when large air volumes are to be provided, for instance in the case of large-area LAF ceilings where different flow velocities are also required. Furthermore a vertical downward air flow can also be cooled accordingly using a suitable air conditioning system (e.g. using an air cooling recirculation module). LED lighting systems or all-around media supply bridges can also be included in the concept.

Systems with laminar flow primarily use HEPA filters (high efficiency particulate air filters) or ULPA filters (ultra low penetration air filters). Filter units spread across the entire protective zone contribute to a reduction of the initial filter pressure resulting from the high filter surface area. Filters are always to be regularly inspected for leakage and replaced where necessary.

The aim is to ensure the highest possible levels of protection for patients and the surgical team in the operating theatre or any other medical facility. Only optimally aligned air filtering components can provide highest levels of sterility and so contribute to a reduction of dangerous airborne particles and germs and any resulting post-operative infections. Consequences such as a longer recovery phase, prolongation of hospital stay or increase in mortality risk are to be minimised. To this end Marchhart designs a clean air concept tailored to match your operating theatre requirements where the desired room class, flow type and direction, air velocity and room temperature are all taken into account.

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Laminar flow is short for laminar air flow (LAF). This laminar air flow ensures that airflow cleaned through filters is directed as far as possible into the protective zone without any swirling, i.e. at low turbulence.

A large field of application of this flow system is the medical sector where a stable protective zone must be established and contaminated air discharged in a targeted manner. Large laminar flow ceilings are especially required in operating theatres.

Maximum sterility must be guaranteed in operating theatres, as well as hazardous airborne particles and germs reduced with a focus on preventing postoperative infections. The provided supply air is cleaned through HEPA filters and directed as a laminar flow to a protective zone around the operating table. To achieve an as uniform as possible air flow the filtered supply air is fed through the CG laminariser (CG distributor), a special nylon fabric, into the room.

The air in the protective zone itself is inevitably contaminated by a large number of germs or particles (e.g. by the surgical team, microorganisms and germs, bacteria…) so immediate extraction is essential (wall or floor suction). If large scale LAF ceiling systems require the use of various air flow velocities, it can be used as differential flow according to DIN 1946-4 (2018-09).

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The main area of application for CG laminarisers (CG distributors, fabric frames) is the operating theatre where a stable protective zone must be provided. This stable protective zone can only offer maximum protection for both patients and the surgical team when it uses laminar flow (low turbulence displacement flow, LAF). To this end laminarisers are used as outlets towards the operating theatre. A CG fabric frame is comprised of an aluminium profile and mostly covered on both sides with special nylon fabrics. 

The air purified through the appropriate filters in the LAF ceiling system is directed vertically downwards through the CG distributors to create a protective zone. The contaminated air from the protective zone is discharged through the floor.

Depending on the room class and protective zone requirements a single side covering of the mesh frame may be effective. Use as differential flow according to DIN 1946-4 is possible to achieve different air flow velocities. For this purpose the CG distributor is only covered single sided in the "core area” and double sided all around. This results in a higher outflow velocity in the core area and lower outflow velocity in the outer area (= differential flow).

Advantages of a CG laminariser (CG distributor, fabric frame)
•    Size of the mesh frames depends on the project
•    Different flow optimised frames
•    Production in purest conditions
•    Mesh replacement in case of soiling/contamination or damage
Selecting the right weave (mesh size, thread density) is decisive for achieving optimal laminar flow. This laminar flow can prevent germs and particles from contaminating the sterile protective zone of an operating theatre. Dedicated stretching tables with large stretching surfaces are required to span this high quality special mesh over the frames. Precision and cleanliness must be ensured during the entire process.

Repair any damage
CG laminarisers must be regularly cleaned to prevent any impairment of their functionality. Should the special mesh be damaged, it must be repaired by a specialist since otherwise germs and particles might enter the protective zone and hence pose a risk.

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A hybrid operating theatre is a modern theatre additionally equipped with angiography, CT or MR imaging devices.* 
Imaging techniques using mobile C-arms, ultrasound and endoscopy have long been standard in the operating theatre; today higher image quality and intra-operative rotation angiography are in demand.* The size of a hybrid operating theatre also has to be adjusted to reflect the additional equipment and the larger surgical team. (*Source: Wikipedia)

Marchhart offers various customised approaches addressing your operating theatre requirements and complete ventilation systems where optimised lighting (for the operative field and ambient light) is also included. The supply air ceiling construction is adapted according to whether the imaging equipment is intended to be ceiling mounted, floor standing or mobile.

Hybrid operating theatre with ceiling mounted system
Ceiling mounted C-arms require two rails to be mounted in line with structural conditions on the ceiling, along which the system can be moved back and forth. The great advantage is that the operating table with the patient including tubes and catheters remains fixed and does not have to be moved.

Hybrid operating theatre with floor standing system
Ceiling mounted C-arms do however affect the laminar air flow and particles could fall off the moving parts over the operative field into the wound. In accordance with the required hygiene standard it may be better to use a floor-standing unit. A floor mounted unit relieves the supply system integrated in the ceiling used to operate various monitors and equipment. A floor mounted C-arm however also means that the operating table has to be moved, often representing a challenge for patient care and anaesthesia.

Hybrid operating theatre with a mobile floor-bound system
Moving a mobile C-arm across the floor is relatively simple in comparison, it moves sideways along the patient and does not interfere with anaesthesia.

No matter which system is used, hybrid operating theatre facilities provide access to the entire imaging equipment during operation, allowing many procedures to be keep minimally invasive. For the patients this means a less invasive operating method with smaller surgical wounds and thus a shorter healing phase. With Marchhart air filtering technology we have a right solution for any system currently on the market.

>> Go to News for photos of various hybrid operating theatres equipped with Marchhart air filter technology

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A supply air ceiling (also supply air filtering ceiling) is required for rooms where the indoor climatic air conditions such as concentration of airborne particles, temperature, humidity and pressure are to be continuously monitored and ensured while providing the total required air volume through a room air conditioning system. Different air handling components or their combinations are used to reflect the varying room requirements. The aim is to provide clean air, create a stable protective zone for the work area or the entire room and ensure controlled discharge of contaminated air. The required air is fed into the protective zone through the supply air filtering ceiling in a downward flow and can also be cooled by an air conditioning system if required.

Large area supply air filtering ceiling
A continuous laminar flow is achieved for the entire zone area through a large-area supply air filtering ceiling; the high density housing design is adjusted to meet the existing room structure. Terminally placed mesh frame elements ensure the necessary uniform air discharge at up to 0.45m/s.
Nodes integrated in the mesh frame layer provide for installation of monitoring components (air velocity or temperature sensors) and/or sprinkler system elements. The integrated HEPA filters provide the necessary filtering of the supply air. LED backlighting can also be provided in the supply air filtering ceiling. Appropriate test connections and hoses are integrated to allow testing of system safety and performance of DEHS filter leakage tests.

Compact supply air filtering ceiling
Work zones often have different requirements regarding air purity. To address such requirements, zones with higher clean room requirements are equipped with a compact supply air ceiling. This design includes an enclosed housing structure with integrated HEPA filter and terminal mesh frame elements and if required also perforated sheet diffuser elements. It is also possible to use an energy-efficient design with integrated free-wheeling fans in recirculation mode and associated control systems. The test connections for AEROSOL sampling and application as well as LED indicators of operating modes are also integrated for the required leakage testing.

For an extended installation the airflow to the supply air filtering ceiling can also include a recirculation wall module with a pre-filter. The module includes an integrated air cooler/heater and corresponding control system for air preparation with optional LED indicators for operating modes.

Supply air filtering ceilings are used in a variety of areas, for instance in the foodstuffs industry or laboratories; when required the design of the components for the compact supply air filtering ceiling can also include increased explosion protection pursuant to the ATEX Directive 2014/34/EU (for the zones 1, 2, 21 and 22).

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>> Go to the product details for compact supply air filtering ceilings with fan

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A recirculated air ceiling is primarily used where a large protective zone is required despite a low proportion of fresh air. The solution is a mix of purified fresh air and filtered recirculated air. The stale room air is extracted (ideally at floor level) and mixed with the supply air from outside. Heat loads generated by personnel and technical equipment can be sensibly used to control air temperature through a plenum system in the recirculation module. The recirculated air ceiling system with its laminar air flow creates a stable protective zone providing the highest level of safety and air quality. It protects against contamination by airborne particles and germs and hence complies with the highest hygienic requirements.

Air conditioning system with dry cooling
Air conditioning systems with dry cooling preventing condensation and hence increased hygienic risks in the recirculated ceiling are used to provide desired room temperature and humidity. Furthermore, mixing cooler outside air with warmer recirculated air from the operating theatre or a clean room creates a pleasant climate also without an integrated cooling system. After mixing the air is blown back as clean air into the room through a filter system; the uniformity of the air flow is ensured by terminally placed mesh frame elements. The required protective zone is created through the downward laminar flow.

Recirculated air ceiling in the operating theatre
The operation theatre where the operative field, the surgical team as well as instruments and implants must be protected is the main area for using these ceilings. Best conditions are created for performing sensitive operations (hip respectively joint operations, operations with foreign body implants, etc.). The laminar flow recirculated air ceiling is also suitable for the instrument prep zones or recovery rooms as well as in production of pharmaceuticals.
The laminar flow recirculation ceiling is installed compactly in the false ceiling as a high-density system. The recirculated air ceiling modules arranged at the sides lead the room air directly to the pressure chamber. If there is no space for recirculated air ceiling modules, then the recirculated air wall modules are used. Energy efficient recirculated air ceilings are equipped with integrated fans to be able to supply large operating theatre ceiling fields also when the fresh air proportion is low. The entire air volume is blown through HEPA filters and supplied sterile to the operating theatre protective zone as laminar flow; optionally as differential flow with higher core and lower edge velocities.

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Reflecting different room requirements various air handling components or their combinations are selected, primarily in compliance with the standard DIN 1946-4, which is the currently valid German standard for room class H1a. Laminar flow achieves in H1a clean rooms significantly lower germ and particle contaminations in the operative field and on the instruments table when compared to turbulent mixed ventilation. In H1b rooms (for operations with less high risk of infection) recirculation equipment dilutes the airborne germ and particle concentration by supplying filtered air which mixes with the contaminated room air. Optionally, recirculated air ceilings can be equipped with LED backlighting, media bridges and connections for medical equipment.

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The recirculated air cooling module unit is an independently operating system suitable especially for removal of heat loads and particle reduction in laboratories, clean rooms and production zones. In combination with a heat exchanger, two filtering stages (fine dust F7 or F9) and a HEPA filter stage (H13 or H14) this component represents an air conditioning system suitable for use in clean rooms. A separate control cabinet provides for control of this module.
As a compact air conditioning module for air circulation within the room it is equipped with the major air treatment features (pre-filtering, silencer, heat exchanger, HEPA filters and optionally a heater); it is comprised of an aluminium housing in high-density and corrosion-resistant design and allows the use of different diffuser elements (perforated sheet diffuser, swirl diffuser, nozzle diffuser, mesh diffuser). The "EASY-CLICK" system used to open and close the fluff separators provides for simple and fast filter replacement or cleaning without any tools; version with fall protection. Due to the use of terminal HEPA filters this component complies with the hygienic requirements for deployment in clean rooms.
The standard version is designed as a ceiling module for horizontal installation in the false ceiling. Alternatively, it can be also vertically mounted in the wall. A design version as a visible room element is also possible.

Recirculated air module for cool rooms:
these modules can be also used as special version for cool rooms. This module is suitable for both cool rooms with down to -5°C (cooling level I) and deep-freeze rooms down to -20°C (cooling level II). The control cabinet provides the central facility management system with a multitude of functions and information. Optionally, the recirculated air modules can be additionally equipped with a control panel or signalling information directly on the module. It can be installed directly in the clean room in dependency with the desired application.

Recirculated air module with explosion protection:
when required this component can also be designed with increased explosion protection compliant with the ATEX Directive 2014/34/EU (for zones 1, 2, 21 and 22).

Recirculated air cooling module unit:
+ Tightly welded aluminium housing
+ High density and corrosion resistant design
+ Disinfectant resistant surface coating
+ Integrated test connection for DEHS aerosol leakage testing and/or differential pressure monitoring
+ Flush mounting on the visible side 
+ Various diffuser elements with a simple EASY CLICK system
+ Fine dust filter cell class M5-M9 (plastic frame) as a pre-filter
+ HEPA filter class H13-H14 (aluminium frame) as main filter
+ Heat exchanger, optionally with condensate drip tray, for room cooling and heat load dissipation 
+ Mounting of speed-controlled centrifugal fans on a vibration-damping construction elements
+ Sound absorbing baffles for the necessary sound reduction in the intake and discharge areas
+ Optional LED signalling lamp for system check
+ Optional system extension with an additional heating coil
+ Optional comfort control with control panel for data information

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Recirculated air filtering systems are used where tasks are to be additionally performed under specific ventilation conditions. This is for instance when sampling various materials and substances required for production of medicines. The recirculated air filtering systems are hence primarily used in the pharmaceutical sector and laboratories but also in industry. Multitudes of dusty materials and gaseous substances are inflammable under certain conditions. The ventilation component system of the recirculating unit must therefore comply with EX protective zone requirements and have explosion-proof design.
Recirculating systems are independently functioning complete systems which can be individually planned and structurally integrated into any room. 
They are comprised of the following main components:

  • Supply air filtering ceiling
  • Recirculated air cooling module
  • "SAFE CHANGE" duct filter casing
  • Control systems engineering
  • Necessary recirculation duct elements (incl. silencers) 

These optimally aligned components provide for a corresponding protective zone. Additionally, also stabilising curtains or laminated safety glass sliding doors as well as floor extractors can be considered to accordingly direct the air flow and feed it into the system in a targeted manner.
The control panel for the recirculated air filtering system is individually designed to match the customer requirements and wishes.

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Clean rooms require an air purity in line with the respective required room class. For this purpose the air is to be filtered with terminally positioned HEPA (H13 or H14) filters prior to it entering the room. The filters are installed in compact pharmaceutical casings (also referred to as pharmaceutical diffusers) either in the false ceiling or in the wall where they are customised to match the room conditions. The required turbulent mixed ventilation (TMS) is achieved by using the appropriate diffuser elements (swirl diffuser, perforated sheet diffuser, nozzle diffuser). The diffusers are always installed flush, and a wide range of sizes and types is available (e.g. with/without test groove or gel filter). The test connections for AEROSOL application (supply air) and CLEAN AIR sampling are also integrated for the required leakage testing. When required extremely large filter elements can be installed without difficulty. 

Pharmaceutical filter casing as a combination casing
Sensitive production areas possibly require clean rooms to have a higher clean room classification making customisation of the construction and design of the pharmaceutical casing necessary. Individual casings are arranged in series and integrated in channel grid or cross channel grid ceilings to create a continuous inflow area. The air is then distributed in the room through the terminally positioned mesh frame diffuser. Backlighting can be optionally integrated.

Marchhart uses the "EASY-CLICK" mounting system providing comfortable and quick removal or installation of the fluff filter guard and fluff filter as well as the diffuser elements for maintenance or filter change by using the "EASY-CLICK" lock - saving time and requiring no tools.

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The duct filter casing serves as a high-density filter unit for air filtering directly in the duct network or supply of particle free and germ free air to hygienic areas (hospital, pharmaceutical sector, clean rooms). The duct filter casing is installed in a technical area to facilitate access to the filter making maintenance possible without entering the clean rooms. 
Area of application pursuant to the standards EN ISO 14644, ÖNORM H 6020, DIN 1946-4 for medical purposes respectively VDI 2083 and for all clean rooms as set forth by the Directive PIC/S_PE 009-11.
Accordingly, the duct connection design to the actual clean room must be completely airtight. The housing itself is of airtight design and is equipped with a maximum of two subsequent filtering stages and integrated filter test groove. Testing connections for AEROSOL application and optionally for clean air sampling with appropriate test lances 

"SAFE CHANGE" filter unit
Substances hazardous to health are used in some clean rooms. An airtight duct filter unit with integrated maintenance technology is used to prevent any contact during maintenance. This allows filter replacements and maintenance to be performed without any health hazards.
A "SAFE CHANGE" duct filter casing can also be integrated in clean room discharge air cabinets for safe, contact-free filter replacement using maintenance bag technology. The wall-mounted discharge cabinet is placed directly in the room to discharge the extraction air, the individual "SAFE CHANGE" filters are maintained using dedicated inspection openings. For hygienic reasons the inspection door on the visible side is used to access the filters.

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The constantly growing demands on modern industry with ever more precise technologies require innovative clean air solutions compliant with all current standards, providing for safety of processes, products and people, while operating energy-efficiently, sustainably and quietly.
Filtering air of harmful contaminations, airborne particles and microorganisms protects staff from health risks during work, products from contamination, quality degradation or cross-contamination, and the environment from hazardous substances. At the same time the air is regulated according to requirements for temperature, humidity and flow and the extraction air is discharged in a targeted manner. This creates a “clean workplace” where work can be performed under the best possible conditions.

Clean air systems in industry are primarily used:

  • In chemical sectors
  • In pharmaceutical sectors
  • In microelectronics
  • In foodstuffs technology
  • In space research
  • In laboratories and
  • In genetic engineering

In the foodstuffs sector production with low germ levels can extend the shelf life of the products. In laboratories care has long been taken to provide for clean air so that research results are not falsified. Microelectronics has the highest demands for ultra-clean air. Optimal air conditions ensure that even the smallest microchips and other components remain free of defects during production and hence the highest product quality is achieved.

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