11-HVAC

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HVAC Guidelines: 

HVAC Guidelines

HVAC -Introduction: 

HVAC -Introduction Heating, ventilation and air-conditioning (HVAC) play an important role in ensuring the manufacture of quality pharmaceutical products. A well designed HVAC system will also provide comfortable conditions for operators.

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The focus on recommendations for systems for manufacturers of solid dosage forms. Refer to other systems or components which are not relevant to solid dosage form manufacturing plants, but which may assist in providing a comparison between the requirements for solid dosage-form plants and other systems.

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HVAC system design influences architectural layouts with regard to items such as airlock positions, doorways and lobbies. The architectural components have an effect on room pressure differential cascades and cross-contamination control.

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The prevention of contamination and cross-contamination is an essential design consideration of the HVAC system. In view of these critical aspects, the design of the HVAC system should be considered at the concept design stage of a pharmaceutical manufacturing plant.

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Temperature, relative humidity and ventilation should be appropriate and should not adversely affect the quality of pharmaceutical products during their manufacture and storage, or the accurate functioning of equipment. Aims to give guidance to pharmaceutical manufacturers and inspectors of pharmaceutical manufacturing facilities on the design, installation, qualification and maintenance of the HVAC systems.

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These guidelines are intended to complement those provided in Good manufacturing practices for pharmaceutical products (1) and in conjunction with the parent guide. The additional standards addressed by the present guidelines should therefore be considered supplementary to the general requirements set out in the parent guide.

Scope of document: 

Scope of document These guidelines focus primarily on the design and good manufacturing practices (GMP) requirements for HVAC systems for facilities for the manufacture of solid dosage forms. Most of the system design principles for facilities manufacturing solid dosage forms also apply to other facilities such as those manufacturing liquids, creams and ointments.

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These guidelines do not cover requirements for manufacturing sites for the production of sterile pharmaceutical products. These guidelines are intended as a basic guide for use by GMP inspectors. They are not intended to be prescriptive in specifying requirements and design parameters. There are many parameters affecting a clean area condition and it is, therefore, difficult to lay down the specific requirements for one particular parameter in isolation.

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Many manufacturers have their own engineering design and qualification standards and requirements may vary from one manufacturer to the next. Design parameters should, therefore, be set realistically for each project, with a view to creating a cost-effective design, yet still complying with all regulatory standards and ensuring that product quality and safety are not compromised. The three primary aspects addressed in this manual are the roles that the HVAC system plays in product protection, personnel protection and environmental protection (Fig. 1).

guidelines address: 

guidelines address GMP MANUFACTURING ENVIRONMENT Contamination (product & staff) Prevent contact with dust Avoid dust discharge Protect from product cross-contamination Prevent contact with fumes Avoid fume discharge

guidelines address: 

guidelines address Correct temperature & humidity Acceptable comfort conditions Avoid effluent discharge SYSTEMS SYSTEM VALIDATION PRODUCT PROTECTION PERSONNEL PROTECTION ENVIRONMENT PROTECTION

Definitions: 

Definitions acceptance criteria Measurable terms under which a test result will be considered acceptable. action limit The action limit is reached when the acceptance criteria of a critical parameter have been exceeded. Results outside these limits will require specified action and investigation.

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air-handling unit (AHU ) The air-handling unit serves to condition the air and provide the required air movement within a facility. airlock An enclosed space with two or more doors, which is interposed between two or more rooms, e.g. of differing classes of cleanliness, for the purpose of controlling the airflow between those rooms when they need to be entered. An airlock is designed for and used by either people or goods (PAL, personnel airlock; MAL, material airlock). alert limit The alert limit is reached when the normal operating range of a critical parameter has been exceeded, indicating that corrective measures may need to be taken to prevent the action limit being reached.

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as-built Condition where the installation is complete with all services connected and functioning but with no production equipment, materials or personnel present. at-rest Condition where the installation is complete with equipment installed and operating in a manner agreed upon by the customer and supplier, but with no personnel present.

Definations: 

Definations central air-conditioning unit (see air-handling unit) change control A formal system by which qualified representatives of appropriate disciplines review proposed or actual changes that might affect a validated status. The intent is to determine the need for action that would ensure that the system is maintained in a validated state.

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clean area (clean room) 1 An area (or room) with defined environmental control of particulate and microbial contamination, constructed and used in such a way as to reduce the introduction, generation and retention of contaminants within the area. Commissioning Commissioning is the documented process of verifying that the equipment and systems are installed according to specifications, placing the equipment into active service and verifying its proper action. Commissioning takes place at the conclusion of project construction but prior to validation.

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Containment A process or device to contain product, dust or contaminants in one zone, preventing it from escaping to another zone. Contamination The undesired introduction of impurities of a chemical or microbial nature, or of foreign matter, into or on to a starting material or intermediate, during production, sampling, packaging or repackaging, storage or transport.

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critical parameter or component A processing parameter (such as temperature or humidity) that affects the quality of a product, or a component that may have a direct impact on the quality of the product. cross-contamination Contamination of a starting material, intermediate product or finished product with another starting material or material during production.

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design condition Design condition relates to the specified range or accuracy of a controlled variable used by the designer as a basis for determining the performance requirements of an engineered system. design qualification (DQ) DQ is the documented check of planning documents and technical specifications for conformity of the design with the process, manufacturing, GMP and regulatory requirements. Note: Clean area standards, such as ISO 14644-1 provide details on how to classify air cleanliness by means of particle concentrations, whereas the GMP standards provide a grading for air cleanliness in terms of the condition (at-rest or operational), the permissible microbial concentrations, as well as other factors such as gowning requirements.

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direct impact system A system that is expected to have a direct impact on product quality. These systems are designed and commissioned in line with good engineering practice (GEP) and, in addition, are subject to qualification practices. facility The built environment within which the clean area installation and associated controlled environments operate together with their supporting infrastructure.

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good engineering practice (GEP) Established engineering methods and standards that are applied throughout the project life-cycle to deliver appropriate, cost-effective solutions. indirect impact system This is a system that is not expected to have a direct impact on product quality, but typically will support a direct impact system. These systems are designed and commissioned according to GEP only. Infiltration Infiltration is the ingress of contaminated air from an external zone into a clean area.

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installation qualification (IQ) IQ is documented verification that the premises, HVAC system, supporting utilities and equipment have been built and installed in compliance with their approved design specification. no-impact system This is a system that will not have any impact, either directly or indirectly, on product quality. These systems are designed and commissioned according to GEP only. non-critical parameter or component A processing parameter or component within a system where the operation, contact, data control, alarm or failure will have an indirect impact or no impact on the quality of the product.

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normal operating range The range that the manufacturer selects as the acceptable values for a parameter during normal operations. This range must be within the operating range. operating limits The minimum and/or maximum values that will ensure that product and safety requirements are met. operating range Operating range is the range of validated critical parameters within which acceptable products can be manufactured.

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operational condition This condition relates to carrying out room classification tests with the normal production process with equipment in operation, and the normal staff present in the room. operational qualification (OQ) OQ is the documentary evidence to verify that the equipment operates in accordance with its design specifications in its normal operating range and performs as intended throughout all anticipated operating ranges.

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oral solid dosage (OSD ) Usually refers to an OSD plant that manufactures medicinal products such as tablets, capsules and powders to be taken orally. performance qualification (PQ) PQ is the documented verification that the process and/or the total process related to the system performs as intended throughout all anticipated operating ranges. point extraction Air extraction to remove dust with the extraction point located as close as possible to the source of the dust. pressure cascade A process whereby air flows from one area, which is maintained at a higher pressure, to another area at a lower pressure.

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Qualification Qualification is the planning, carrying out and recording of tests on equipment and a system, which forms part of the validated process, to demonstrate that it will perform as intended. relative humidity The ratio of the actual water vapour pressure of the air to the saturated water vapour pressure of the air at the same temperature expressed as a percentage. More simply put, it is the ratio of the mass of moisture in the air, relative tothe mass at 100% moisture saturation, at a given temperature.

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standard operating procedure (SOP) An authorized written procedure, giving instructions for performing operations, not necessarily specific to a given product or material, but of amore general nature (e.g. operation of equipment, maintenance and cleaning, validation, cleaning of premises and environmental control, sampling and inspection). Certain SOPs may be used to supplement product-specific master and batch production documentation. turbulent flow Turbulent flow, or non-unidirectional airflow, is air distribution that is introduced into the controlled space and then mixes with room air by means of induction.

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unidirectional airflow (UDAF) Unidirectional airflow is a rectified airflow over the entire cross-sectional area of a clean zone with a steady velocity and approximately parallel streamlines (see also turbulent flow). (Modern standards no longer refer to laminar flow, but have adopted the term unidirectional airflow.) Validation The documented act of proving that any procedure, process, equipment, material, activity or system actually leads to the expected results.

validation master plan (VMP) : 

validation master plan (VMP) VMP is a high-level document which establishes an umbrella validation plan for the entire project, and is used as guidance by the project team for resource and technical planning (also referred to as master qualification plan).

Protection: 

Protection Product and personnel Areas for the manufacture of pharmaceuticals, where pharmaceutical starting materials and products, utensils and equipment are exposed to the environment, should be classified as “clean areas”. The achievement of a particular clean area classification depends on a number of criteria that should be addressed at the design and qualification stages. A suitable balance between the different criteria will be required in order to create an efficient clean area.

Basic Criteria includes: 

Basic Criteria includes building finishes and structure air filtration air change rate or flushing rate room pressure location of air terminals and directional airflow ow temperature humidity material flow personnel flow equipment movement

PowerPoint Presentation: 

process being carried out outside air conditions occupancy type of product. Air filtration and air change rates should ensure that the defined clean area classification is attained. The air change rates should be determined by the manufacturer and designer, taking into account the various critical parameters. Primarily the air change rate should be set to a level that will achieve the required clean area classification.

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Air change rates normally vary between 6 and 20 air changes per hour and are normally determined by the following considerations: level of protection required the quality and filtration of the supply air particulates generated by the manufacturing process particulates generated by the operators configuration of the room and air supply and extract locations sufficient air to achieve containment effect sufficient air to cope with the room heat load sufficient air to maintain the required room pressure.

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In classifying the environment, the manufacturer should state whether this is achieved under “as-built” , “at-rest” or “operational” conditions. Supply air Return air

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Room classification tests in the “Operational” Condition “as-built” condition should be carried out on the bare room, in the absence of any equipment or personnel.

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Room classification tests in Supply air the “at-rest” condition should be carried out with the equipment operating where relevant, but without any operators. Because of the amounts of dust usually generated in a solid In operation dosage facility most clean area classifications are rated for the “at-rest” condition.

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Room classification tests in the “operational” condition should be carried out during the normal production Return Process with equipment operation Air and the normal number of personnel present in the room. Generally a room that is tested for an “operational” condition should be able to be cleaned up to the “at-rest” clean area classification after a short clean-uptime. The clean-up time should be determined through validation and is generally of the order of 20 minutes.

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Materials and products should be protected from contamination and cross-contamination during all stages of manufacture for cross-contamination control. Note: contaminants may result from inappropriate premises (e.g. poor design, layout or finishing), poor cleaning procedures, contaminants brought in by personnel, and a poor HVAC system. Airborne contaminants should be controlled through effective ventilation. External contaminants should be removed by effective filtration of the supply air (See Fig. 5 for an example of a shell-like building layout to enhance containment and protection from external contaminants.)

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Internal contaminants should be controlled by dilution and flushing of contaminants in the room, or by displacement air flow . Airborne particulates and the degree of filtration should be considered critical parameters with reference to the level of product protection required. The level of protection and air cleanliness for different areas should be determined according to the product being manufactured, the process being used and the product’s susceptibility to degradation

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Filter classes should always be linked to the standard test method because referring to actual filter efficiencies can be very misleading (as 57 different test methods each result in a different value for the same filter) In selecting filters, the manufacturer should have considered other factors, such as particularly contaminated ambient conditions, local regulations and specific product requirements. Good prefiltration extends the life of the more expensive filters downstream.

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Comparison of filter test standards Rough comparison between the different filter standards (filter classes should always be connected to the standard test method). EN, European norm (Euro norm); EU, European Union. EU Class EN 779 & EN 1822 99.9999 5 U16 99.9995 U15 14 99.995 H14 13 99.95 H13 12 11 99.5 H12 10 95 H11 9 95 85 F9/H10 8 90 75 F8 85 F7 7 80 75 6 70 F6 65 ,60 ,55 ,50 .5 F5 , 45 (average) 40 , 35 ,4 95 30 G4 90 25,3 85 20 G3 80 ,75 ,2 70 G2 65 G1 EN 1822 EN 779 Percentage (average) Percentage (integral value) Eurovent Class – Eurovent 4/5 (2-9) , Eurovent 4/9 (2-9) , Eurovent 4/4 (10-14) Dust spot efficiency ASHRAE 52/76 ,BS6540 Part 1 (1985)MPPS, DEHS Aerosol EN1822 ,CEN/TC/195 ,WG1-G1-F9 ,WG2-H10-16 Arrestance (%) Percentage

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Materials for components of an HVAC system should be selected with care so that they do not become the source of contamination. Any component with the potential for liberating particulate or microbial contamination into the air stream should be located upstream of the final filters. Ventilation dampers, filters and other services should be designed and positioned so that they are accessible from outside the manufacturing areas (service voids or service corridors) for maintenance purposes

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Personnel should not be a source of contamination. Directional airflow within production or packing areas should assist in preventing contamination. Airflows should be planned in conjunction with operator locations, so as to minimize contamination of the product by the operator and also to protect the operator from dust inhalation. HVAC air distribution components should be designed, installed and located to prevent contaminants generated within the room from being spread

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Supply air diffusers of the high induction type (e.g. those typically used for office-type air-conditioning) should where possible not be used in clean areas where dust is liberated. Air diffusers should be of the non-induction type, introducing air with the least amount of induction so as to maximize the flushing effect Whenever possible, air should be exhausted from a low level in rooms to help provide a flushing effect.

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Unidirectional airflow Swirl diffuser (recommended) Unidirectional airflow (UDAF) should be used where appropriate to provide product protection by supplying a clean air supply over the product, minimizing the ingress of contaminants from surrounding areas. Where appropriate, the unidirectional airflow should also provide protection to the operator from contamination by the product.

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Sampling of materials such as starting materials, primary packaging materials and products, should be carried out in the same environmental conditions that are required for the further processing of the product. In a weighing booth situation, the aim of the design using UDAF should be to provide dust containment. A dispensary or weighing booth should be provided with unidirectional airflow for protection of the product and operator. The source of the dust and the position in which the operator normally stands should be determined before deciding on the direction of unidirectional flow.

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The dust generated at the weighing station is immediately extracted through the perforated worktop, thus protecting the operator from dust inhalation, but at the same time protecting the product from contamination by the operator by means of the vertical unidirectional airflow stream. The unidirectional flow velocity should be such that it does not disrupt the sensitivity of balances in weighing areas. Where necessary the velocity may be reduced to prevent inaccuracies during weighing, provided that sufficient airflow is maintained to provide containment.

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The position in which the operator stands relative to the source of dust liberation and airflow should be determined to ensure that the operator is not in the path of an airflow that could lead to contamination of the product

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Once the system has been designed and qualified with a specific layout for operators and processes, this should be maintained in accordance with an SOP. There should be no obstructions in the path of a unidirectional flow air stream that may cause the operator to be exposed to dust. The incorrect use of a weighing scale which has a solid back. The back of the weighing scale should not block the return air path as this causes air to rise vertically, resulting in a hazardous situation for the operator.

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Where an open bin is placed below a vertical unidirectional flow distributor. The downward airflow should be prevented from entering the bin, and then being forced to rise again, as this would carry dust up towards the operator’s face. solid worktop can sometimes cause deflection of the vertical unidirectional airflow resulting in a flow reversal. A possible solution would be to have a 100 mm gap between the back of the table and the wall, with the air being extracted here.

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Under this concept the air should be supplied to the corridor, flow through the doorway, and be extracted from the back of the cubicle. Normally the cubicle door should be closed and the air should enter the cubicle through a door grille, although the concept can be applied to an opening without a door. The velocity should be high enough to prevent turbulence within the doorway resulting in dust escaping.

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This displacement airflow should be calculated as the product of the door area and the velocity, which generally results in fairly large air quantities. Pressure differential concept (high pressure differential, low air flow) Note: The pressure differential concept may normally be used in zones where little or no dust is being generated. It may be used alone or in com

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The high pressure differential between the clean and less clean zones should be generated by leakage through the gaps of the closed doors to the cubicle. The pressure differential should be of sufficient magnitude to ensure containment and prevention of flow reversal, but should not be so high as to create turbulence problems.

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In considering room pressure differentials, transient variations, such as machine extract systems, should be taken into consideration. Note: The most widely accepted pressure differential for achieving containment between two adjacent zones is 15 Pa, but pressure differentials of between 5 Pa and 20 Pa may be acceptable. Where the design pressure differential is too low and tolerances are at opposite extremities, a flow reversal can take place. For example, where a control tolerance of ± 3 Pa is specified, the implications of the upper and lower tolerances on containment should be evaluated.

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The pressure differential between adjacent rooms could be considered a critical parameter, depending on the outcome of risk analysis. The limits for the pressure differential between adjacent areas should be such that there is no risk of overlap, e.g. 5 Pa to 15 Pa in one room and 15 Pa to 30 Pa in an adjacent room, resulting in no pressure cascade, if the first room is at the maximum tolerance and the second room is at the minimum tolerance. Low pressure differentials may be acceptable when airlocks (pressure sinks or pressure bubbles) are used.

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The pressure control and monitoring devices used should be calibrated and qualified. Compliance with specifications should be regularly verified and the results recorded. Pressure control devices should be linked to an alarm system set according to the levels determined by a risk analysis, Manual control systems, where used, should be set up during commissioning and should not change unless other system conditions change. Airlocks can be important components in setting up and maintaining pressure cascade systems. Airlocks with different pressure cascade regimes include the cascade airlock, sink airlock and bubble airlock (Figs 19–21). Cascade airlock: high pressure on one side of the airlock and low pressure on the other. Sink airlock: low pressure inside the airlock and high pressure on both outer sides.

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Bubble airlock: high pressure inside the airlock and low pressure on both outer sides. Doors should open to the high pressure side, and be provided with self-closers. Door closer springs if used, should be designed to hold the door closed and prevent the pressure differential from pushing the door open. Sliding doors are not recommended. Central dust extraction systems should be interlocked with the appropriate air handling systems, to ensure that they operate simultaneously. Room pressure imbalance between adjacent cubicles which are linked by common dust extraction ducting should be prevented.

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Air should not flow from the room with the higher pressure to the room with the lower pressure, via the dust extract ducting (this would normally occur only if the dust extraction system was inoperative). Physical barrier concept Where appropriate, an impervious barrier to prevent cross-contamination between two zones, such as barrier isolators or pumped transfer of materials, should be used. Spot ventilation or capture hoods may be used as appropriate.

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Temperature and relative humidity should be controlled, monitored and recorded, where relevant, to ensure compliance with requirements pertinent to the materials and products, and to provide a comfortable environment for the operator where necessary. Maximum and minimum room temperatures and relative humidity should be appropriate. Temperature conditions should be adjusted to suit the needs of the operators while wearing their protective clothing. The operating band, or tolerance, between the acceptable minimum and maximum temperatures should not be made too close. Cubicles, or suites, in which products requiring low humidity are processed, should have well-sealed walls and ceilings and should also be separated from adjacent areas with higher humidity by means of suitable airlocks. Precautions should be taken to prevent moisture migration that increases the load on the HVAC system.

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Humidity control should be achieved by removing moisture from the air, or adding moisture to the air, as relevant. Dehumidification (moisture removal) may be achieved by means of either refrigerated dehumidifiers or chemical dehumidifiers. Appropriate cooling media for dehumidification such as low temperature chilled water/glycol mixture or refrigerant should be used. Dehumidifiers should be avoided if possible as they may become a source of contamination (e.g. microbiological growth). Where humidification is required, this should be achieved by appropriate means such as the injection of steam into the air stream. A product-contamination assessment should be done to determine whether pure or clean steam is required for the purposes of humidification.

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Where steam humidifiers are used, chemicals such as corrosion inhibitors or chelating agents, which could have a detrimental effect on the product, should not be added to the boiler system. Humidification systems should be well drained. No condensate should accumulate in air-handling systems. Other humidification appliances such as evaporative systems, atomizers and water mist sprays, should not be used because of the potential risk of microbial contamination. Duct material in the vicinity of the humidifier should not add contaminants to air that will not be filtered downstream.

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Air filters should not be installed immediately downstream of humidifiers. Cold surfaces should be insulated to prevent condensation within the clean area or on air-handling components. When specifying relative humidity, the associated temperature should also be specified. Chemical driers using silica gel or lithium chloride are acceptable, provided that they do not become sources of contamination.

Dust control : 

Dust control Wherever possible, the dust or vapour contamination should be removed at source. Point-of-use extraction, i.e. as close as possible to the point where the dust is generated, should be employed. Point-of-use extraction should be either in the form of a fixed high velocity extraction point or an articulated arm with movable hood or a fixed extraction hood. Dust extraction ducting should be designed with sufficient transfer velocity to ensure that dust is carried away, and does not settle in the ducting.

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The required transfer velocity should be determined: it is dependent on the density of the dust (the denser the dust, the higher the transfer velocity should be, e.g. 15–20 m/s). Airflow direction should be carefully chosen, to ensure that the operator does not contaminate the product, and so that the operator is not put at risk by the product. Dust-related hazards to which the operators may be subjected should be assessed. An analysis of the type of dust and toxicity thereof should be done and the airflow direction determined accordingly. Point extraction alone is usually not sufficient to capture all of the contaminants, and general directional airflow should be used to assist in removing dust and vapours from the room.

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Typically, in a room operating with turbulent airflow, the air should be introduced from ceiling diffusers and extracted from the room at low level to help give a flushing effect in the room. The low-level extraction should assist in drawing air downwards and away from the operator’s face. The extract grilles should be positioned strategically to draw air away from the operator, but at the same time to prevent the operator from contaminating the product. When planning the system for the extraction of vapours, the density of the vapour should be taken into account. If the vapour is lighter than air, the extract grilles should be at a high level, or possibly at both high and low levels.

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When dealing with particularly harmful products, additional steps, such as handling the products in glove boxes or using barrier isolator technology, should be used. When working with exposed products such as hormones or highly potent products, operators should wear totally enclosed garments The air supply to this type of breathing apparatus should normally be through an air compressor. Filtration, temperature and humidity need to be controlled to ensure operator safety and comfort.

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The rates at which fresh air is supplied to the facility should comply with national, regional and/or international regulations, to provide operators with an acceptable level of comfort and safety and also to remove odours or fumes. The rate of fresh airflow should also be determined by leakage from the building, for pressure control purposes.

Protection of the environment : 

Protection of the environment Dust in exhaust air Exhaust air discharge points on pharmaceutical equipment and facilities, such as from fluid bed driers and tablet-coating equipment, and exhaust air from dust extraction systems, carry heavy dust loads and should be provided with adequate filtration to prevent contamination of the ambient air. Where the powders are not highly potent, final filters on a dust exhaust system should be fine dust filters with a filter classification of F9 according to EN779 filter standards.

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Where harmful substances such as penicillin, hormones, toxic powders and enzymes are manufactured, the final filters on the dust exhaust system should be HEPA filters with at least an H12 classification according to EN1822 filter standards, as appropriate. For exhaust systems where the discharge contaminant is considered particularly hazardous, it may be necessary to install two banks of HEPA filters in series, to provide additional protection should the first filter fail

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When handling hazardous compounds, safe-change fitter housings, also called “bag-in-bag-out” filters, should be used. All filter banks should be provided with pressure differential indication gauges to indicate the filter dust loading. Filter pressure gauges should be marked with the clean filter resistance and the change-out filter resistance. Exhaust filters should be monitored regularly to prevent excessive filter loading that could force dust particles through the filter media, or could cause the filters to burst, resulting in contamination of the ambient air.

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Sophisticated computer-based data monitoring systems may be installed, with which preventive maintenance is planned by trend logging (This type of system is commonly referred to as a building management system (BMS), building automation system (BAS) or system control and data acquisition (SCADA) system.) An automated monitoring system should be capable of indicating any out-of-specification condition without delay by means of an alarm or similar system. Where reverse-pulse dust collectors are used for removing dust from dust extraction systems, they should usually be equipped with cartridge filters containing a compressed air lance, and be capable of continuous operation without interrupting the airflow.

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Alternative types of dust collectors (such as those operating with a mechanical shaker, requiring that the fan be switched off when the mechanical shaker is activated) should be used in such a manner that there is no risk of cross-contamination. There should be no disruption of airflow during a production run as the loss of airflow could disrupt the pressure cascade. Mechanical-shaker dust collectors should not be used for applications where continuous airflow is required. When wet scrubbers are used, the dust-slurry should be removed by a suitable drainage system.

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The quality of the exhaust air should be determined to see whether the filtration efficiency is adequate with all types of dust collectors and wet scrubbers. Where necessary, additional filtration may be provided downstream of the dust collector. Fume removal The systems for fume, dust and effluent control should be designed, installed and operated in such a manner that they do not become possible sources of contamination or cross-contamination, e.g. an exhaust-air discharge point located close to the HVAC system fresh air inlet. Fumes should be removed by means of wet scrubbers or dry chemical scrubbers (deep-bed scrubbers).

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Wet scrubbers for fume removal normally require the addition of various chemicals to the water to increase the adsorption efficiency. Deep-bed scrubbers should be designed with activated carbon filters or granular chemical adsorption media. The chemical media for deep-bed scrubbers should be specific to the effluent being treated. The type and quantity of the vapours to be removed should be known to enable the appropriate filter media, as well as the volume of media required to be determined.

HVAC systems and components: 

HVAC systems and components The required degree of air cleanliness in most OSD manufacturing facilities can normally be achieved without the use of high-efficiency particulate air (HEPA) filters, provided the air is not recirculated. Many open product zones of OSD form facilities are capable of meeting ISO 14644-1 Class 8, “at-rest” condition, measured against particle sizes of 0.5 µm and 5 µm, but cleanliness may not be classified as such by manufacturers.

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There should be no failure of a supply air fan, return air fan, exhaust air fan or dust extract system fan. Failure can cause a system imbalance, resulting in a pressure cascade malfunction with a resultant airflow reversal.

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Air should be dried with a chemical drier (e.g. a rotating desiccant wheel which is continuously regenerated by means of passing hot air through one segment of the wheel). The figure illustrates the chemical drier handling part of the fresh air/return air mixture on a by-pass flow. The location of the chemical drier should be considered in the design phase. Examples of appropriate locations include: — full flow of fresh/return air; — partial handling of fresh/return air (by-pass airflow); — return air only; — fresh air only; or — pre-cooled air with any of the above alternatives.

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Possible additional components that may be required should be considered depending on the climatic conditions and locations. These may include items such as: — frost coils on fresh air inlets in very cold climates to preheat the air; — snow eliminators to prevent snow entering air inlets and blocking airflow; — dust eliminators on air inlets in arid and dusty locations; — moisture eliminators in humid areas with high rainfall; and — fresh air pre-cooling coils for very hot or humid climates. Appropriate alarm systems should be in place to alert personnel if a critical fan fails.

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Appropriate alarm systems should be in place to alert personnel if a critical fan fails. Low-level return or exhaust air grilles are usually preferred. However, where this is not possible, a higher air change rate may be needed to achieve a specified clean area classification, e.g. where ceiling return air grilles are used. There may be alternative locations for return air. For example, referring to Fig. 24, room D (low-level return air) and room E (ceiling return air). The airflow schematics of the two systems (Figs 24 and 25) indicate air-handling units with return air or recirculted air, having a percentage of fresh air added. Fig. 25 is a schematic diagram of an air-handling system serving rooms with horizontal unidirectional flow, vertical unidirectional flow and turbulent flow, for rooms A, B and C, respectively. The airflow diagram in Fig. 24 is an example of a typical system with a lower clean area classification.

PowerPoint Presentation: 

Horizontal unidirectional flow, vertical unidirectional flow and turbulent fl w Air-handling unit Fresh air = Return air = Supply air Cooling coil HEPA filters Supply air fan Primary filter Re-heater HEPA filter Room A Production room with horizontal UDAF 0.45 m/s Production room with vertical UDAF 0.3 m/s Production room with low-level return Room B ROOM C Secondary filter UDAF, unidirectional airflow; HEPA, high-efficiency particulate air.

Recirculation system : 

Recirculation system There should be no risk of contamination or cross-contamination (including by fumes and volatiles) due to recirculation of air. Depending on the airborne contaminants in the return-air system it may be acceptable to use recirculated air, provided that HEPA filters are installed in the supply air stream to remove contaminants and thus prevent cross-contamination. The HEPA filters for this application should have an EN1822 classification of H13.