diff --git a/mlair/helpers/filter.py b/mlair/helpers/filter.py
index b6c27cbcb781e4593a8533ab2ac72928fecadb67..2fe95ebbab05ecf096a7a0c03469c16378716826 100644
--- a/mlair/helpers/filter.py
+++ b/mlair/helpers/filter.py
@@ -466,6 +466,7 @@ class ClimateFIRFilter:
 
             # select only values at tmp dimension 0 at each point in time
             coll.append(filt.sel({new_dim: 0}, drop=True))
+            gc.collect()
 
         logging.info(f"{data.coords['Stations'].values[0]}: concat all variables")
         res = xr.concat(coll, var_dim)