diff --git a/daq.c b/daq.c
index 681bfd5..d935834 100644
--- a/daq.c
+++ b/daq.c
@@ -39,7 +39,7 @@ int DAQ(int t_hrs, int sp_s)
   FILE* dfp;                                    // create a file pointer
   const char data_header[200] =
       "t\tCO2\tCO2 f\tCO\tCO f\tO2\tO2\tT CO\tT O2\tP CO\tP O2\tRH\n"\
-      "s\tppm\tppm\tppm\tppm\tppm\t%\t°C*10\t°C\tmBar\tmBar\t%";
+      "s\tppm\tppm\tppm\tppm\tppO2\t%\t°C*10\t°C\tmBar\tmBar\t%";
   char co2_uf[10]="",   co2_f[10]="",
                 co_uf[10]="",    co_f[10]="",
                 o2_ppm[10]="",   o2_xcent[10]="",