8 Network Data Return

8.1 POLLUTION YEAR CALENDAR

The Network is operated according to a long-established "Pollution Year calendar". The Pollution Year always begins on the Tuesday nearest to 1st April, and contains twelve months, each of exactly 4 or 5 weeks, all beginning on Tuesdays (to minimise problems with public holidays, which often occur on Mondays). The months are arranged to correspond as closely as possible to calendar months. Weeks are numbered. The year is divided into "summer" (April to September) and "winter" (October to March). Data from the Network are processed in batches corresponding to one Pollution Calendar month, and the site operators receive a monthly printout of results.

8.2 DATA RETURN FORM

In order to ensure that all site operators send their results for processing in a consistent format, a standard data return form is used. These pre-printed forms, are issued monthly by AEA Technology Environment. The data return form is two-sided. The front is for data entry, the back contains instructions for completion; the front and back are shown in Fig. 8.1 and 8.2 respectively.

The form should be completed according to the instructions on the back. Please do your best to return your completed forms within 2 weeks of the end of the month shown at the top of the form, and no later than 4 weeks after the end of the month. Forms arriving later than this will have to be processed separately, and it could be several months before you get the results printouts.

If at all possible, the operator should take the Data Return Form to the sites when they are visited, and record the gas meter reading directly onto the form. Likewise, titration results and reflectometer readings should be recorded on the form at the time these measurements are made. This avoids transcription errors. However, if this is not possible, a log book should be kept in which the above data can be recorded. All entries should identify the site and date. The log book should be used for this purpose only, and great care should be taken when results are copied onto the form.

Please bear the following points in mind when completing the form:

• Please use black or dark blue pen, not pencil or red.
• Please include the name and full telephone number (including the area code) of the people who actually took the measurements.
• Please record measurements directly on the form, not from rough notes (to avoid transcription errors).
• Figures should not be entered in the shaded areas of the form.
• Please write clearly, with one digit per box.
• Mistakes should be rectified neatly using correcting fluid.
• If there is any malfunction of the equipment through loss of power supply or pump or timer failure, or blockage of the air supply, please write a note in the "Comments" column, on the right-hand side of the form.
• If there are bonfires in the immediate vicinity, or pollution of the local atmosphere through fumes or dust raised by building or road construction workers, this should be noted in the ‘Comments’ column.
• Do not write notes or other extraneous data within the solid green boxes, except in the space reserved for comments.
• If the site was out of operation for the entire month, fill in the form as for a site breakdown and make a note explaining the circumstances.
• Take a copy of the completed form before sending it to AEA Technology Environment. Most operators have access to a photocopier, but AEA Technology Environment still supply two copies of each form so that a carbon copy can be made if necessary.

• The maximum gap between meter readings is 8 full 24-hour periods. In practice, this means the sampler will need to be visited every week.
• If more than 8 24-hour periods elapse between site visits, the first and eighth days’ results will be lost due to double exposure.
• Please enter the time of the meter reading to the nearest minute.
• Do not forget to complete the "last meter reading in previous month" and "next meter reading" boxes if applicable.
• Please check air volume flow-rates weekly to ensure that they are within the acceptable range of 1.8 to 2.2 m³ per day (65 to 75 cubic feet per day). This works out at around 14 m³ (500 cubic feet) per week. If this is done while at the site, mis-readings can be corrected, and faults identified quickly.
• Check that all times and meter reading are entered against the day they were actually taken.
• If the meter is changed, complete the form as instructed on the back.

• When the meter has to be changed, there will be two meter readings on the day of the change: one from the old meter, and one from the new. The old meter’s reading must be entered in the usual way. That from the new meter must be written at the foot of the form, in the section marked ‘1^st New Meter’ which also includes space for the clamp size. In order to draw the attention of the data entry operator to the meter change, the letter M is placed in the box for clamp size, the day following the change.
• If the meter was changed twice, complete the ‘2^nd New Meter’ box also.
• If the old meter read in cubic feet, and the new one is metric, please fill in the ‘M/F’ box at the top of the form as for the old meter, but make a note in the "Comments" column to alert AEA Technology Environment to this.

• Please remember to complete the "clamp size" column.
• The clamp size required is the diameter of the stain in inches, not of the outside of the filter clamp. In most, but not all cases this is now 1. This column must not be left blank.
• Where N is entered in the reflectometer box, (no valid reflectometer reading) then the clamp box must also be N.
• If there appears to be no stain, as occasionally happens, the reflectometer reading should be entered as 99, not 100 or 00. Check that air has, in fact, been drawn through the filter and that there are no loose connections through which air could be drawn without passing through the filter. Alternatively, the inlet tube may have become loose, allowing clean indoor air to be drawn in.

• If, when indicator is added to the exposed solution, it is exactly the same neutral grey as the unexposed colour control, write 0.0 in the titration box.
• If, when indicator is added to the exposed solution, it is blue, write ALK in the titration box. If more than 5 ALK readings occur during the month, make a note in the RHS margin, and check for possible reasons.

8.4 COMMON ERRORS

Certain errors occur frequently; these are listed below.

• Meter readings of 5 digits instead of 4, or not in the correct format.
• Meter readings entered with the decimal point in the wrong place.
• Time and meter readings entered on the wrong date line, one day out.
• Clamp figures missing.
• Gaps of more than 8 days between meter readings
• Failure to carry forward to the new form (in the space marked "Last meter reading in previous month") the final time and meter reading of the period just ending.
• Failure to enter in the ‘Next meter reading’ boxes at the foot of the page, the first time and meter reading of the next new form (this is not necessary if the last Monday on the form has a ‘Time’ and ‘Meter Reading’ entry).
• Absence of full telephone numbers (especially the telephone area code) of responsible staff.

Certain criteria have been adopted in the computer validation program so that no calculations can be carried out when the results would, in effect, be meaningless. The main safeguards are as follows;

• Checks for invalid times, meter readings, clamp sizes, reflectometer readings, titrations.
• Checks for missing times, meter readings, clamp sizes, reflectometer readings, titrations.
• Checks that correct month’s data is being processed
• Gaps of over 8 days between meter readings
• Air volumes of less than 1.80 m³per 24 hours (63 cubic feet per 24 hours), or more than 2.18 m³per 24 hours (77 cubic feet per 24 hours): these will cause data to be rejected.
• For single day sites only - continuous running on one filter and bubbler for more than 3 days cannot be regarded as giving reliable average and the readings are rejected. In this connection it should be noted that the concentrations given in the printed daily results immediately following the letter "C" must be taken as applying to these "C" days as well, since they represent the average pollution over the whole of the 2 or 3 days concerned.
  

Also, the following occurences are highlighted for attention, as they may indicate an error or a problem:

• Any reflectometer reading less than 40
• Large increases in reflectometer reading or titration between one day and the next.
• Large decreases in reflectometer reading or titration between one day and the next.
• Flowrates greater than 2.15 but less than 2.20m³per day are flagged as ‘A’ (above optimum flowrate) but the data are not rejected.
• Flowrates greater than 2.20m³per day (77 cubic feet per day) are flagged as ‘H’ (high flowrate) and the data are rejected.
• Flowrates less than 1.85 but greater than 1.80m³per day are flagged as ‘B’ (below optimum flowrate) but the data are not rejected.
• Flowrates less than 1.80m³per day (63 cubic feet per day)are flagged as ‘L’ (low flowrate) and the data are rejected.
• A period of low flowrate immediately followed by a period of high flowrate, or vice versa: this usually indicates a time and meter reading has been entered on the data return form one day late or early.

AEA Technology Environment are committed to maximising data capture from the UK Smoke and SO₂ Network, and the efforts made by site operators to avoid breakdowns are greatly appreciated. Regular maintenance, and weekly checks of sampling flowrate reduce the likelihood of breakdowns and provide early warning of problems before they become serious. It is useful to keep spare components if possible; in particular, if a Capex pump is in use, the site operator should keep a spare filter and critical orifice assembly to hand. If an equipment breakdown occurs, please fill in the data return form as instructed on the back.

It is also greatly appreciated if measurements can be kept up over the Christmas holiday when heavy pollution is not unusual. It is usually possible to make an extra site visit before the holidays, so that unattended periods of more than 7 days can be avoided.