diff --git a/lark1fq/main.c b/lark1fq/main.c
index ba79c08..18b2f9b 100755
--- a/lark1fq/main.c
+++ b/lark1fq/main.c
@@ -30,6 +30,7 @@ void device_init(void)
 {
     flag.filter = data_ltc1867.calc_flag;
     flag.concentration = flag.filter;
+    flag.gas_fault = 0xFFFFFFFF;
 }
 
 void system_init(void)
diff --git a/lark1fq/src/device.c b/lark1fq/src/device.c
index 1e3c095..98834ff 100755
--- a/lark1fq/src/device.c
+++ b/lark1fq/src/device.c
@@ -102,7 +102,11 @@ const uint8_t * const modbus_map_ro[] = {
     [OFFSET_MAIN + 61] = (uint8_t *)(&bitmap_main->gasn_avail_bitmap) + 2,
     [OFFSET_MAIN + 62] = (uint8_t *)(&bitmap_main->gasn_avail_bitmap) + 1,
     [OFFSET_MAIN + 63] = (uint8_t *)(&bitmap_main->gasn_avail_bitmap) + 0,
-    [(OFFSET_MAIN + 64) ... (OFFSET_MAIN + 511)] = (uint8_t *)0,
+    [OFFSET_MAIN + 64] = (uint8_t *)(&flag.gas_fault) + 3,
+    [OFFSET_MAIN + 65] = (uint8_t *)(&flag.gas_fault) + 2,
+    [OFFSET_MAIN + 66] = (uint8_t *)(&flag.gas_fault) + 1,
+    [OFFSET_MAIN + 67] = (uint8_t *)(&flag.gas_fault) + 0,
+    [(OFFSET_MAIN + 68) ... (OFFSET_MAIN + 511)] = (uint8_t *)0,
 
     [OFFSET_GAS1 + 0] = (uint8_t *)(&bitmap_main->gas1_sub_id) + 3,
     [OFFSET_GAS1 + 1] = (uint8_t *)(&bitmap_main->gas1_sub_id) + 2,
diff --git a/lark1fq/src/device.h b/lark1fq/src/device.h
index c8e9a51..4646211 100755
--- a/lark1fq/src/device.h
+++ b/lark1fq/src/device.h
@@ -177,6 +177,7 @@ struct flag_s {
     uint32_t filter;
     uint32_t concentration;
     uint32_t filter_climb;
+    uint32_t gas_fault;
 };
 
 extern const uint8_t * const modbus_map_ro[];
diff --git a/lark1fq/src/filter.c b/lark1fq/src/filter.c
index 1414839..af9e3a7 100755
--- a/lark1fq/src/filter.c
+++ b/lark1fq/src/filter.c
@@ -175,6 +175,69 @@ void filter_window_process(void)
     }
 }
 
+static int flag_for_sig_init_error(uint8_t ch, uint32_t sig)
+{
+    const struct lookup_table_s *p; /* just for reduce text char in code */
+    float temp, temp_quantum;
+    float k; /* delta_b = y1 + (y2 - y1) / (x2 - x1) * (temp - x1) */
+    float sig_fixed;
+    uint8_t idx_t = 0; /* temperature index */
+
+    if (data_gas_info.id[ch] == GAS_ID_INVALID) {
+        return 0;
+    }
+    /* step1: initialization variable  */
+    p = &((*bitmap_gas)[ch].lookup_table);
+    temp = (float)(device_data.detector_temperature);
+
+    /* step2: get temperature index */
+    for (idx_t = 0; idx_t < p->temperature_points; idx_t++) {
+        if (temp < p->detector_temperature[idx_t]) {
+            break;
+        }
+    }
+    if (idx_t == 0) {
+        idx_t = 1; /* temperature is less than lowest temperature */
+    } else if (idx_t >= p->temperature_points) {
+        idx_t = p->temperature_points - 1; /* temperature is more than highest temperature */
+    } else {
+        /* calc with linear relation */
+    }
+
+    /* step3: calc const variable of temperature */
+    temp = temp - p->detector_temperature[idx_t - 1];
+    temp_quantum = p->detector_temperature[idx_t] - p->detector_temperature[idx_t - 1];
+
+    /* step4: calc sig0 value by temperature */
+    k = ((float)(p->sig[0][idx_t]) - (float)(p->sig[0][idx_t - 1])) / temp_quantum;
+    sig_fixed = k * temp + p->sig[0][idx_t - 1];
+
+    /* laset sig > sig_fixed * 80% */
+    if (sig < sig_fixed * 0.8f) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+static void flag_for_sig_init_error_process(void)
+{
+    uint32_t flag_fault = 0xFFFFFFFF;
+
+    for (uint8_t ch = 0; ch < 4; ch++) {
+        if (data_gas_info.id[ch] == GAS_ID_INVALID) {
+            flag_fault |= (1 << ch);
+            continue;
+        }
+        if (flag_for_sig_init_error(ch, data_filter[ch].window_output)) {
+            flag_fault |= (1 << ch);
+        } else {
+            flag_fault &= ~(1 << ch);
+        }
+    }
+    flag.gas_fault = flag_fault;
+}
+
 void filter_output_process(void)
 {
     if (flag.filter_climb > 0) {
@@ -186,10 +249,13 @@ void filter_output_process(void)
                 flag.filter_climb--;
             }
         }
+        if (flag.filter_climb == 0) {
+            flag_for_sig_init_error_process();
+        }
         return;
     }
     for (uint8_t i = 0; i < 4; i++) {
-        if (data_gas_info.id[i] == 0xFFFFFFFF) {
+        if (data_gas_info.id[i] == GAS_ID_INVALID) {
             device_data.gas_sig[i] = 0;
         } else {
             device_data.gas_sig[i] = data_filter[i].window_output;