Design, Development, Layout

The plan shows a suggested layout for a 100 m2 square conditioned area which can be adapted to other shapes and sizes. The following points should be considered when organising fittings and services.

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• Benching should ideally be epoxy coated and fully sealed. Formica kitchen type worktops can be used if of high quality and well fitted with good seals between sections.

• Some low level benching should be considered to accommodate universal testers. This will give more convenient access to the cross head and upper clamps.

• The balance table should be secured only to the floor and not to the walls. This reduces vibration. If the floor is springy then a mineral slab, e.g. paving stone, should be let into the floor for the balance table to stand on.

• Double electric outlets should be provided at 1.5 m centres on all benches. Note also the sample cutting and measuring table will also need electrical outputs either in the floor below, or more conveniently, suspended from the ceiling.

• Take advice from the suppliers of the air conditioning system as to the services needed for the unit. Typically it will require its own dedicated electricity supply which may be three phase for larger capacity systems. Access to mains water to feed the humidifier may be required although some systems incorporate a reservoir rather than direct plumbing.

• Ensure the sample conditioning shelves are located in an area where there is free circulation of air so as to avoid anomalous conditions developing locally.

• Lighting should be standard fluorescent type.

• Grey areas in plan show benches. These should have storage below but ensure that there is adequate provision for workers to sit with knees under benches. Chairs have been shown on the plan where this is particularly relevant. The use of free standing benches which can be relocated easily is recommended.

• Some equipment, e.g. universal testers with pneumatic clamps, may need compressed air. This should ideally be provided from a compressor located outside the laboratory so as to minimise noise.

• There should be a back up generator if the mains supply is unreliable. See elsewhere for discussion of alternative strategies. The key issue is that sample conditioning requirements normally specify 24 hours under standard conditions. If the atmospheric control is lost it can take several hours to regain equilibrium so continuous runnig is preferable.

Air Conditioning Systems-Requirements and Control

The atmosphere controlled part of the laboratory must comply with ISO 139 for textile testing and ISO 2419 for leathers.

The standard atmosphere and their tolerance zone are as shown below.

The 20/65 atmosphere is the one normally adopted for textile work. The alternative 23/50 should only be used if asked for by the client. In practice this will happen rarely. The atmospheres are not intended to be equivalent but simply reflect different standards.

The 23/50 atmosphere is more commonly used for leather testing but 20/65 is also acceptable. Laboratories carrying out testing on both matrices will typically adopt 20/65. The conditioning and working atmosphere used should be recorded on reports of the testing.

The atmospheric conditions must be monitored by traceably calibrated equipment with the minimum performance parameters shown in the table below. Note that these instruments must be independent of the air conditioning control system monitors.

The air handling system must be able to control the temperature and humidity within the tolerance zone. Bearing in mind the uncertainty of measurement, this means that temperature must be controlled to within ±1.5°C and humidity to within ±2% RH of the required value if the actual tolerance or specifications are to be met.

This level of control requires a specialised air conditioning system. Conventional air conditioners, whatever claims are made by suppliers, will not provide adequate control.A key issue is that the system will have to be capable of increasing humidity in the laboratory. This requires a steam generator which is not part of normal air conditioners.
The most reliable approach is to purchase a pre-packaged system from one of the specialist suppliers of textile equipment. This consists of a unit which is mounted in the laboratory and a unit which is fixed outside. Suppliers will often provide installation but it is easily accomplished by any local air conditioning specialist.
If it is decided to use a local air conditioning firm to design and install a system, rather than to use a pre-packaged unit, then it is essential that the chosen contractor has previous experience of providing high precision systems for laboratories and industry. The laboratory should obtain a list of the systems previously supplied by potential contractors and should insist on visiting some of the installations and discussing their performance with the users.
There is unfortunate history of laboratories accepting assurances from potential suppliers as to the level of control which can be achieved with conventional, and seductively low cost, air conditioners and then finding they have a system which cannot deliver the performance needed once it is installed. The recriminations and re-engineering required then result in loss of time and considerable expense.
The capacity of the air conditioner required needs to be carefully determined. It is preferable to ensure that the capacity is at least 25% in excess of what is actually required so as to ensure the unit is not over strained.
The key factors to be considered are shown below.

• The volume of the laboratory.

• The sum total heat output of equipment in the laboratory assuming simultaneous operation.

• The type of construction and thickness of walls and ceilings and the extent to which they provide a seal from surrounding areas. The seal should be maximised.

• The heating and air conditioning in adjoining rooms and typical temperatures.

• Number of doors to the laboratory.

• Whether there are windows to the outside environment.

• The local meteorological conditions especially the winter low and summer high temperature and humidity.

• The number of people normally working in the laboratory and the number of hours worked.

This information should enable an air conditioning engineer to calculate the capacity of system needed. Providers of pre-packaged systems will typically provide a questionnaire, see below for an example, so the laboratory can list all relevant information in a convenient form. The supplier will then be able to quote for a unit of suitable capacity.

Monitoring of Atmospheric Conditions

The air conditioning system will normally have a readout of the temperature and humidity being achieved and will also display the settings. This readout, even if traceably calibrated, is not adequate for provision of a record of the conditions actually being achieved in the laboratory for the following reasons.

• It will only record the temperature and humidity at the location of the air handling unit so provided no information on the uniformity of the conditions throughout the laboratory.

• The measurement is not independent of the control system as required by clause 4.2 of ISO 139:2005.

• Such systems do not necessarily have the facility to keep a record of fluctuations over time. The laboratory should have a high precision and accuracy temperature/relative humidity meter with traceable calibration carried out annually. It should be able to meet the specifications detailed above. The meter should be checked three monthly by comparing the temperature reading with a reference thermometer reading to 0.1 °C. The humidity calibration should also be verified three monthly by means of a traceably calibrated reference. This can normally be purchased with the meter in the form of a solution in a capsule which can be placed over the probe of the instrument and which will generate a known humidity.

Note that wet and dry bulb systems, including whirling hygrometers, will not meet the requirements of accreditation. They have insufficient precision and cannot be calibrated to adequate uncertainty. Calibration of the thermometers in wet and dry bulb hygrometers, even if traceable, does not constitute a calibration of the humidity measurements. The temperature/humidity meter is used to monitor the atmosphere in the laboratory according to the following pattern.

• Record the temperature and humidity at the start, middle and end of each working day. The measurement should be made as nearly as possible at the central point of the laboratory at work bench height.

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• At least once each week record the temperature and humidity at a minimum of five points throughout the laboratory in the working areas. When selecting the points for monitoring take into account the following.

  • Measurements should all be at working surface height.

  • There should be measurements close to the mid points of each wall and as close as possible to the centre of the laboratory.

  • One of the points should be on the sample conditioning shelves. If this is not achieved by one of the five points described above include an additional point.

  • One of the points should be on a work surface as near as possible to the laboratory door. If this is not achieved by one of the five points described above include an additional point.

  • Measurements should be made during normal working hours when normal operations and staff numbers prevail.

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Suitable example monitoring points are shown on the plan of a typical conditioned area shown above. The record of measurements must show that the required value and range of humidity and temperature is met at every monitoring point. If this is not achieved then steps must be taken to resolve the problem. Fans suitably located will often deal with locally poor air circulation.

In addition the laboratory should have an instrument such as that shown on the left which provides a continuous record of temperature and humidity. The instrument shown provides a weekly chart but a system which stores data electronically can also be used. The recorder must be traceably calibrated annually but need not be of high precision as its purpose is to back up the daily and weekly high precision measurements and to demonstrate that there have been no major fluctuations in the conditions. It will, for example, pick up any effects of power interruptions, especially outside working hours, which might go unnoticed. The instrument can be located any convenient point but should not be close to the air handling system nor near the laboratory door. Ideally the air conditioning system should be run 24/7. This is essential if the laboratory is also used to condition samples. Some laboratories find continuous running unacceptable on the basis of cost and safety considerations. They choose to condition samples in a separate conditioning cabinet, which provides 24/7 standard conditions, and only to run the air conditioning system in the laboratory during working hours.

This strategy is not recommended but if it is adopted the laboratory will have to show that, whenever testing is carried out, the correct atmospheric conditions prevailed. This will require the following measurements and records.

• Thedaily and weekly measurements on the laboratory atmosphere specified above must still be made and recorded. They must conform. In larger laboratories the time needed to establish a correct and uniform atmosphere can extend to several hours.

• The temperature and humidity at the time and location in the laboratory where each test is conducted must be recorded along with each test result. For tests lasting more than 30 minutes the temperature and humidity at the test location at the start and end of testing must be recorded along with the result.

• The sample conditioning chamber must have a temperature and humidity monitor independent of the control system and this must be traceably calibrated and verified regularly. There should also be continuous recording within the chamber to detect any major fluctuations. The uniformity of temperature and humidity in the chamber should be verified every three months.

• Sample conditioning records must still be kept but will be linked to the records for the conditioning chamber not to those of the laboratory as a whole.

If at any time the temperature or humidity in the laboratory is found to be out of specification, either generally or at a particular work location, then any affected work must be suspended pending restoration of the situation. There must be a record showing the time of start and end of the suspension. Before resuming work the uniformity of the temperature and humidity must be established by carrying out the weekly test regime and recording the measurements. The entire record, of out of specification temperature/humidity and its restoration and checking, would constitute a record of non-conforming work in ISO 17025 terms. Any work inadvertently carried out when conditions did not conform must be repeated under conforming conditions.

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Wet Chemistry Area

Layout and Services

This area will only be required by laboratories which are conducting compositional analysis of textiles and leather and/or tests for contaminants. An example of a suitable layout for a laboratory of 50 sq metres is shown below.

If the laboratory is only engaged in relatively basic tests with little instrumentation, perhaps requiring only ultra-violet spectroscopy, then no further chemical testing facilities will be required. However if more extensive instrumentation such as gas chromatographs, mass spectrometers and possibly atomic spectrometry are in use then a separate instrumental facility will be needed.

In designing a wet chemistry laboratory the following points need to be considered.

• Floors should be continuous welded vinyl with a non-slip finish.

• Allow generous fume hood space, at least 2 metres and more if possible. Remember a fume hood will serve as an ordinary bench but not vice versa. Fume hoods will require water, drainage, electrical outlets (at least two per metre) and lighting.

• Provide a segregated dry area for instrumentation.

• Storage for acids, solvents and reagents needs to be vented where possible.

• Always include a separate balance table. Remember any balance of more then three places will need a low vibration environment so ensure table is anchored to floor and standing free from walls. If the floor is springy provide a solid base by letting a paving stone or similar into the floor. Make sure the balance table is not near the fume hood to avoid air currents.

• Provide under bench storage but ensure each bench has a at least one space to allow sitting with legs under the bench.

• Provide for double electrical outlets every metre on all benches. On island benches these should run down the centre line of the bench on upstands.

Water Purifier

This needs to be chosen carefully. It must generate water compatible with ISO 3696 Grade 2. The options are ion exchange, reverse osmosis and distillation. Consider the following points.

• Distillation is only suitable for small amounts of water; volumes of the order of five to ten litres per day will be possible but no more. In practice most applications, e.g. trace metals analysis, will require double distillation, so this capacity is further reduced. Distillation is a high energy process but does not require consumables.

• Deionisers have capacities up to 500 litres per day which is a realistic level of demand for most laboratories. Deionisers are can be rapidly overloaded, however, by highly mineralised feed waters and will need frequent replacement of cartridges. Deionisers have zero energy consumption.

• Reverse osmosis systems can produce very high volumes of water easily up to 2000 litres per day. Reverse osmosis systems will have a high consumables demand with highly mineralised feeds so consumables use can be high as with deionisers. It is always advisable to have a reverse osmosis system fitted with a pre-treatment phase using ion exchange as ion exchange cartridges are much cheaper to replace than reverse osmosis membranes. There should also be a pre-filter passing only particles of <4 µm. Reverse osmosis have some energy consumption but this is not significant. It does, however, have a water consumption of the order of 5 to 10 times the volume of water produced so this might be an issue where water supply is expensive or limited.

In practice laboratories will find reverse osmosis with pre-treatment is the best option unless the feed water is of low mineralisation (<50 ppm total dissolved solids) or if there is a major water supply issue. When choosing a system it is essential that the suppliers be advised of the feed water quality and the output per day required and are asked to provide guidance on pre-treatment options and level of consumable consumption expected.

For normal laboratory operations 50 to 100 litres per day will be adequate. The system should be purchased with a storage tank for half a day’s supply. Always request a booster pump for a reverse osmosis system as this will give extra speed of operation helping with high demand.

If the laboratory has high purified water consumption equipment then the reverse osmosis system should be specified with the necessary capacity. Examples of such equipment are Xenon arc and other types of weathering testers and corrosion and humidity cabinets. In very poor mains water quality areas it may be necessary to treat water for use in reference washing applications so this should also be allowed for if appropriate.

In general buy a reverse osmosis system with of the order of twice the capacity which you think you need at present to allow for abnormal operating situations and future expansion.

Any water purification system should be fitted with an on line conductivity meter and should also be checked daily with a traceably calibrated off line meter. It is also useful to monitor pH as this can give a general indication of any change in water quality.

Fume Hoods and their Applications

The typical uses of the fume hood in the textile and leather testing laboratory will be to house extraction and digestion equipment. Applications will include protein determinations, wool content, the extraction of trace contaminants from leather and textiles and digestions for metals analysis. The applications should be supplied in detail to the contractor so that a hood of appropriate construction and materials is supplied. Generally speaking hoods specified for acids will be the most expensive but will be, effectively, general purpose. Hoods specified for organic solvents may not be acid resistant. Hood for work with acids should be specified with a wash down facility as this will increase their life considerably.

Fume hoods are usually manufactured to order from a list of options. Normally lighting will come as standard but you will have to specify water supply, drainage and electrical outlets. A useful standard specification is to ask for compliance with EN 14175. this covers a whole range of safety options but, crucially, the minimum face velocity to be generated as shown in the table below.

This specification will effectively dictate the fan size needed to be supplied. Fans should always be located outside the laboratory so as to minimise noise.

Fume hoods with no discharge to atmosphere are available. They use recirculating filters which require regular changing. Unless it is impossible to discharge to atmosphere, e.g. in a highly populated urban environment, then this type of hood is not recommended. Maintenance costs are high due to the need to change the filters and such hoods are not normally so efficient as direct discharge types.

If a recirculating hood is being used then the application must be specified in detail so that appropriate filters are supplied. Separate hoods will be required for organics and acid work if maximum effectiveness of filters is to be achieved.

Laboratories carrying out a large amount of extraction or distillation work involving cooling water for condensers should seriously consider having the fume cupboard supplied by a closed loop water system with a refrigerated recirculator. This will avoid the large water consumption associated with the use of normal tap water as coolant.

Chemistry Instrument Facility

Laboratories which only have a small amount of simple instrumentation can locate it in the main chemistry area. However if the laboratory has any instrumentation more complex than a simple colorimeter then a separate instrument room should be provided. Instruments which might be located here include chromatographs and atomic spectrometers.

It is also recommended that a separate area be set aside for preparation and storage of standard solutions required for instrument calibration. One of the issues to be confronted in chemical analysis, especially at trace levels, is that the laboratory must, inevitably, have available and handle regularly, in neat form and as solutions, the very compounds being analysed. By confining the preparation of standards to a segregated area the likelihood of contamination of the parts of the laboratory where samples are handled is much reduced. The management rule should be that only the solutions actually required to calibrate instruments should leave the standards preparation room. These will normally be of high dilution so minimising the risk of contamination in the case of a spillage for example. Shown below is a suggested layout for a 50 m2 instrument facility with adjacent standard preparation room.