multiple components which may be merged, comparison of all the spectra from the array is very efficient in discriminating the IS from the PN components. The spectra presented in the next section have been obtained by subtracting the average of the outer pixels from the central pixel. This has little effect on the S/N, and is helpful in reducing the strength of the IS components, especially in cases where they are fairly uniform or have a smooth gradient across the field of the array.

Results
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110 PNe were observed in the survey and 40 were detected. The results of the observations are summarized in Table 1. Column (1) gives the PN name in galactic notation (ordered by galactic longitude); column (2) the common name; column (3) the rms noise level of the observations; columns (4)–(7) the parameters of the CO emission in the cases where the PN is detected (see below); column (8) the heliocentric velocity interval over which there is significant interstellar contamination; and column (9) comments.

The spectra of the PNe in which CO emission is detected or tentatively detected are presented in Fig. 1. It can be seen that the spectra exhibit a large range in 