We have carried out a survey searching for Hα emitting galaxies at z~0.24 using a narrow band filter tuned with the redshifted line. The total sky area covered was 0.19 square degrees within the redshift range 0.228 to 0.255 in a set of four fields in the ELAIS-N1 zone. This corresponds to a volume of 9.8x103Mpc3 and a look-back time of 3.6Gyr when H=50km/s/Mpc and q=0.5 are assumed. A total of 52 objects are selected as candidates for a broad band limiting magnitude of I~22.9, plus 16 detected only in the narrow band image for a narrow band limiting magnitude for object detection of 21.0. The threshold detection corresponds to about 20Å equivalent width with an uncertainty of ~+/-10Å. Point-like objects (15) were excluded from our analysis using CLASS_STAR parameter from SExtractor. The contamination from other emission lines such as [O II]λ3727, Hβ and [OIII]λλ4959,5007 at redshifts 1.2, 0.66 and 0.61 respectively is estimated, and found to be negligible at the flux limits of our sample. We find an extinction-corrected Hα luminosity density of (5.4+/-1.1)x1039erg/s/Mpc3. Our survey for Hα emitting galaxies was carried out using the focal reducer CAFOS at the 2.2 m telescope in CAHA (Centro Astronomico Hispano-Aleman, Almeria, Spain). This instrument is equipped with a 2048x2048 Site#1d CCD with 24μm pixels (0.53" on the sky), which covers a circular area of 16'diameter. (1 data file).