diff --git a/src/array.c b/src/array.c
index 29f5faf..f47c3eb 100644
--- a/src/array.c
+++ b/src/array.c
@@ -404,3 +404,14 @@ signextend (unsigned int value, unsigned int nbits)
 	else
 		return value & mask;
 }
+
+unsigned int
+popcount (unsigned int value)
+{
+	unsigned int count = 0;
+	while (value) {
+		value &= value - 1;
+		count++;
+	}
+	return count;
+}
diff --git a/src/array.h b/src/array.h
index a6ef21e..fab1475 100644
--- a/src/array.h
+++ b/src/array.h
@@ -126,6 +126,9 @@ dec2bcd (unsigned char value);
 unsigned int
 signextend (unsigned int value, unsigned int nbits);
 
+unsigned int
+popcount (unsigned int value);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */
diff --git a/src/shearwater_predator_parser.c b/src/shearwater_predator_parser.c
index b6aa7e2..fc06b66 100644
--- a/src/shearwater_predator_parser.c
+++ b/src/shearwater_predator_parser.c
@@ -118,6 +118,7 @@ typedef struct shearwater_predator_tank_t {
 	unsigned int pressure_reserve;
 	unsigned int serial;
 	char name[2];
+	dc_usage_t usage;
 } shearwater_predator_tank_t;
 
 struct shearwater_predator_parser_t {
@@ -140,6 +141,7 @@ struct shearwater_predator_parser_t {
 	shearwater_predator_tank_t tank[NTANKS];
 	unsigned int tankidx[NTANKS];
 	unsigned int aimode;
+	unsigned int hpccr;
 	unsigned int calibrated;
 	double calibration[3];
 	unsigned int divemode;
@@ -179,6 +181,12 @@ static const dc_parser_vtable_t shearwater_petrel_parser_vtable = {
 };
 
 
+static unsigned int
+shearwater_predator_is_ccr (unsigned int divemode)
+{
+	return divemode == M_CC || divemode == M_CC2 || divemode == M_SC;
+}
+
 static unsigned int
 shearwater_predator_find_gasmix (shearwater_predator_parser_t *parser, unsigned int o2, unsigned int he, unsigned int dil)
 {
@@ -248,9 +256,11 @@ shearwater_common_parser_create (dc_parser_t **out, dc_context_t *context, const
 		parser->tank[i].pressure_reserve = 0;
 		parser->tank[i].serial = 0;
 		memset (parser->tank[i].name, 0, sizeof (parser->tank[i].name));
+		parser->tank[i].usage = DC_USAGE_NONE;
 		parser->tankidx[i] = i;
 	}
 	parser->aimode = AI_OFF;
+	parser->hpccr = 0;
 	parser->calibrated = 0;
 	for (unsigned int i = 0; i < 3; ++i) {
 		parser->calibration[i] = 0.0;
@@ -379,6 +389,7 @@ shearwater_predator_parser_cache (shearwater_predator_parser_t *parser)
 	shearwater_predator_tank_t tank[NTANKS] = {0};
 	unsigned int o2_previous = UNDEFINED, he_previous = UNDEFINED, dil_previous = UNDEFINED;
 	unsigned int aimode = AI_OFF;
+	unsigned int hpccr = 0;
 	if (!pnf) {
 		for (unsigned int i = 0; i < NFIXED; ++i) {
 			gasmix[i].oxygen = data[20 + i];
@@ -490,8 +501,8 @@ shearwater_predator_parser_cache (shearwater_predator_parser_t *parser)
 							tank[id].enabled = 1;
 							tank[id].beginpressure = pressure;
 							tank[id].endpressure = pressure;
-							tank[id].name[0] = i == 0 ? 'D': 'O';
-							tank[id].name[1] = 0;
+							tank[id].usage = i == 0 ? DC_USAGE_DILUENT : DC_USAGE_OXYGEN;
+							hpccr = 1;
 						}
 						tank[id].endpressure = pressure;
 					}
@@ -535,9 +546,17 @@ shearwater_predator_parser_cache (shearwater_predator_parser_t *parser)
 						if (aimode == AI_HPCCR) {
 							for (unsigned int i = 0; i < 2; ++i) {
 								tank[4 + i].enabled = 1;
-								tank[4 + i].name[0] = i == 0 ? 'D': 'O';
-								tank[4 + i].name[1] = 0;
+								tank[4 + i].usage = i == 0 ? DC_USAGE_DILUENT : DC_USAGE_OXYGEN;
 							}
+							hpccr = 1;
+						}
+					}
+				}
+				unsigned int gtrmode = data[offset + 29];
+				if (popcount(gtrmode) >= 2) {
+					for (unsigned int i = 0; i < 4; ++i) {
+						if (gtrmode & (1 << i)) {
+							tank[i].usage = DC_USAGE_SIDEMOUNT;
 						}
 					}
 				}
@@ -659,8 +678,7 @@ shearwater_predator_parser_cache (shearwater_predator_parser_t *parser)
 		for (unsigned int i = 0; i < ngasmixes; ++i) {
 			if (gasmix[i].oxygen == 0 && gasmix[i].helium == 0)
 				continue;
-			if (gasmix[i].diluent &&
-				(divemode != M_CC && divemode != M_CC2 && divemode != M_SC))
+			if (gasmix[i].diluent && !shearwater_predator_is_ccr (divemode))
 				continue;
 			parser->gasmix[parser->ngasmixes] = gasmix[i];
 			parser->ngasmixes++;
@@ -677,6 +695,7 @@ shearwater_predator_parser_cache (shearwater_predator_parser_t *parser)
 		}
 	}
 	parser->aimode = aimode;
+	parser->hpccr = hpccr;
 	parser->divemode = divemode;
 	parser->units = data[parser->opening[0] + 8];
 	parser->atmospheric = array_uint16_be (data + parser->opening[1] + (parser->pnf ? 16 : 47));
@@ -741,21 +760,20 @@ shearwater_predator_parser_get_field (dc_parser_t *abstract, dc_field_type_t typ
 			tank->beginpressure = parser->tank[flags].beginpressure * 2 * PSI / BAR;
 			tank->endpressure   = parser->tank[flags].endpressure   * 2 * PSI / BAR;
 			tank->gasmix = DC_GASMIX_UNKNOWN;
-			switch (parser->tank[flags].name[0]) {
-			case 'S':
-				tank->usage = DC_USAGE_SIDEMOUNT;
-				break;
-			case 'O':
-				tank->usage = DC_USAGE_OXYGEN;
-				break;
-			case 'D':
-				tank->usage = DC_USAGE_DILUENT;
-				break;
-			case 'T':
-			case 'B':
-			default:
-				tank->usage = DC_USAGE_NONE;
-				break;
+			if (shearwater_predator_is_ccr (parser->divemode) && !parser->hpccr) {
+				switch (parser->tank[flags].name[0]) {
+				case 'O':
+					tank->usage = DC_USAGE_OXYGEN;
+					break;
+				case 'D':
+					tank->usage = DC_USAGE_DILUENT;
+					break;
+				default:
+					tank->usage = DC_USAGE_NONE;
+					break;
+				}
+			} else {
+				tank->usage = parser->tank[flags].usage;
 			}
 			break;
 		case DC_FIELD_SALINITY: