CAB80-25 — Page 52

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(2) Industrial Haze.

A circular was addressed by the Ministry of Home Security to local authorities in industrial areas on 20th June requesting them to arrange for factories to emit as much extra smoke as possible without undue loss of production. Following discussions with other Departments concerned on further measures which could be taken for intensifying industrial haze, a second circular was addressed to local authorities on 13th August.

(3) Household grates.

After

In the Prime Minister's original minute on smoke production (see Appendix A) specific reference was made to the burning of smoke producing material in household grates. some considerable experimental work a pitch sawdust briquette was developed. The briquette is designed for use in empty domestic grates; it is broken into five small pieces and burns for half-an-hour.

Large-scale trials with pitch sawdust briquettes were arranged during the August moonlight period with a view to ascertaining the effectiveness of the smoke cloud produced. Briquettes sufficient for two hours' burning were supplied to all householders in Luton and Burslem (40,000 and 15,000 houses respectively) with a request that they should be burned at half- hourly intervals commencing at a given time. Aerial observation was carried out over both towns. The R.A.F. observers' reports were encouraging, but, owing to the fact that the moonlight illumination was reduced by thick low cloud, it was adjudged that only repeat trials could give a conclusive answer to the question whether the household briquette method could be suffessfully applied to screening towns in bright moonlight.

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It

Repeat trials were arranged during the September moonlight periods for four towns - Blackburn (40,000 houses), Halifax (30,000 houses), Burslem (15,000 houses) and Oxford (25,000 houses) to cover the four nights of brightest moonlight. was thought that this would be a safeguard against bad weather and also against the possibility of interference with aerial observation arrangements in consequence of enemy activity. the event, however, the period chosen coincided with severe gales and intensive enemy action and, although the briquettes were burnt according to programme in three of the towns, no aerial observation could be obtained.

In

During the October moonlight period another trial was held at Widnes (14,000 houses), but here again aerial observation was prevented by enemy activity.

Meantime experiments have been continuing with a view to obtaining a smoke-producing material suitable for use on existing coal fires, and which would accordingly be available for the winter months. (The pitch sawdust briquette is designed for use on empty grates and its use on existing fires would be wasteful,) Small-scale experiments with a fuel mixture composed of pitch, naphthalene and coal dust pressed into the shape of the ordinary domestic ovoid have yielded promising results, and the question of large-scale manufacture is being explored as rapidly as possible.

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