C.E.C. Industries Corp., 350 W. 300 South, whose subsidiaries are involved with carbon regeneration and small handyman hardware products, reports a $263,490 loss for the quarter ending Sept. 30, compared to a loss of $142,957 a year ago.

For the six months ending Sept. 30, the company lost $288,498 compared to a loss of $185,522 in the same six months in 1989.A company official said a significant decline in sales to the mining industry and expenditures to position Custom Equipment Corp., the company's principal subsidiary, in the growing carbon regeneration markets were the principal reasons for the increased losses.

Custom serves the mining industry and expects to serve other markets requiring reactivation of granular activated carbon. This carbon has had an increasing role in solutions to environmental problems arising from groundwater remediation, drinking-water contamination and industrial pollutants.

C.E.C. officials have signed a letter of intent with a group of investors by which they will acquire Custom's assets, including rights to the company's technology for use in regenerating carbon. The group will provide the necessary capital so Custom can move ahead in this area.

In return for the transfer by the company of the subsidiary's assets into a new company, C.E.C. will receive a promissory note and a stock interest in the new company.

GLI Industries, another subsidiary of C.E.C., manufactures small handyman hardware products.