This is the application area of regular expressions. If you deliver an example file to parse some more hints might possibly follow.

That's it

 In[1]:= SetDirectory[FileNameJoin[{NotebookDirectory[], "test"}]]
 Out[1]= "N:\\Udo\\Abt_N\\test"

 In[22]:= Select[
          Import["test_file.csv", "Data"], 
          (StringMatchQ[#[[1]], "Type3"] && ((#[[3]] == 1) || (#[[3]] == 6))) &] // Short[#, 17] &

 Out[22]//Short= 
 {{Type3,OK,1,-44.57,-40.68},{Type3,OK,6,-44.6,-41.83},
  {Type3,OK,1,-44.61,-39.72},{Type3,OK,6,-44.53,-41.44},
  {Type3,OK,1,-44.56,-39.92},{Type3,OK,6,-44.58,-40.83},
  {Type3,OK,1,-44.54,-41.47},{Type3,OK,6,-44.51,-41.17},
  {Type3,OK,1,-44.56,-39.89},{Type3,OK,6,-44.57,-41.47},
  {Type3,OK,1,-44.57,-40.62},{Type3,OK,6,-44.55,-41.61},
  {Type3,OK,1,-44.54,-40.41},{Type3,OK,6,-44.57,-41.26},
  {Type3,OK,1,-44.56,-39.98},<<568>>,{Type3,OK,6,-44.72,-41.84},
  {Type3,OK,1,-44.7,-40.06},{Type3,OK,6,-44.7,-40.89},
  {Type3,OK,1,-44.71,-40.85},{Type3,OK,6,-44.69,-42.13},
  {Type3,OK,1,-44.71,-40.68},{Type3,OK,6,-44.73,-41.68},
  {Type3,OK,1,-44.74,-40.77},{Type3,OK,6,-44.71,-41.36},
  {Type3,OK,1,-44.76,-40.94},{Type3,OK,6,-44.78,-41.68},
  {Type3,OK,1,-44.79,-39.98},{Type3,OK,6,-44.75,-42.75},
  {Type3,OK,1,-44.8,-40.52},{Type3,OK,6,-44.8,-41.7}}

Import realizes the CSV format and builds a list per row from which one just selects what's needed.

The result could be exported back to the file system as CSV file, of course.

OMG you turn me back to the eighties ... the following works, but seems by no means faster than the CSV-Import ... have nevertheless fun with it.

Clear[stephensReader]
stephensReader[s_String, a1_String, v1_Integer:1, v2_Integer:6] := 
 Module[{str, r, o = 0, oo = 0, n },
   If[!FileExistsQ[s],
    Print["Sorry, cannot find file \"", s, "\". Bye."];
    Return[$Failed]
   ];
   str = OpenRead[s, BinaryFormat -> True];
   While[True,
    r = ReadLine[str];
    If[r == EndOfFile, Break[], o++, o++];
    r = StringSplit[r, ",", All];
    n = ToExpression[r[[3]]];
    If[StringMatchQ[r[[1]], a1] && ((n == v1) || (n == v2)),
     oo++;
     Print[r]
    ]
   ];
   Close[str];
   Print["Lines read: ", o, " Lines selected: ", oo]
  ] /; StringLength[s] > 0 && StringLength[a1] > 0


stephensReader["test_file.csv", "Type3"]

{Type3,OK,1,-44.57,-40.68}
{Type3,OK,6,-44.6,-41.83}
{Type3,OK,1,-44.61,-39.72}
{Type3,OK,6,-44.53,-41.44}
{Type3,OK,1,-44.56,-39.92}
{Type3,OK,6,-44.58,-40.83}
{Type3,OK,1,-44.54,-41.47}
{Type3,OK,6,-44.51,-41.17}
{Type3,OK,1,-44.56,-39.89}
<snip>
{Type3,OK,6,-44.71,-41.36}
{Type3,OK,1,-44.76,-40.94}
{Type3,OK,6,-44.78,-41.68}
{Type3,OK,1,-44.79,-39.98}
{Type3,OK,6,-44.75,-42.75}
{Type3,OK,1,-44.8,-40.52}
{Type3,OK,6,-44.8,-41.7}

Lines read: 6327 Lines selected: 598

P.S.: The Print of rows is there for demonstration only - stephensReader should as usual return the list of matching rows to be useful.

Clear[stephensReader]
stephensReader[s_String, a1_String, v1_Integer: 1, v2_Integer: 6] := 
 Module[{str, r, o = 0, oo = 0, n, resL = {}},
   If[! FileExistsQ[s],
    Print["Sorry, cannot find file \"", s, "\". Bye."];
    Return[$Failed]
   ];
   str = OpenRead[s, BinaryFormat -> True];
   While[True,
    r = ReadLine[str];
    If[r == EndOfFile, Break[], o++, o++];
    r = StringSplit[r, ",", All];
    n = ToExpression[r[[3]]];
    If[StringMatchQ[r[[1]], a1] && ((n == v1) || (n == v2)),
     oo++;
     resL = Join[resL, {r}];
    ]
   ];
   Close[str];
   Print["Lines read: ", o, "| Lines selected: ", oo];
   resL
 ] /; StringLength[s] > 0 && StringLength[a1] > 0

In[65]:= stephensReader["test_file.csv", "Type3"] // Length
During evaluation of In[65]:= Lines read: 6327| Lines selected: 598
Out[65]= 598

An intermediate approach, use FindList as far as possible, then continue to filter with Select

In[64]:= Select[
  StringSplit[#, ",", All] & /@ FindList["test_file.csv", {"Type3,"}],
   StringMatchQ[#[[3]], "1"] || StringMatchQ[#[[3]], "6"] &] // Length

Out[64]= 598