diff --git a/examples/ccs811/ccs811_one_sensor/ccs811_one_sensor.c b/examples/ccs811/ccs811_one_sensor/ccs811_one_sensor.c
index a53b8a6..df71104 100644
--- a/examples/ccs811/ccs811_one_sensor/ccs811_one_sensor.c
+++ b/examples/ccs811/ccs811_one_sensor/ccs811_one_sensor.c
@@ -174,5 +174,7 @@ void user_init(void)
         // start periodic measurement with one measurement per second
         ccs811_set_mode (sensor, ccs811_mode_1s);
     }
+    else
+        printf("Could not initialize the CCS811 sensor\n");
 }
 
diff --git a/extras/ccs811/README.md b/extras/ccs811/README.md
index fa660ae..3d39ae5 100644
--- a/extras/ccs811/README.md
+++ b/extras/ccs811/README.md
@@ -305,12 +305,14 @@ ccs811_set_mode (sensor, ccs811_mode_1s);
 ...
 ```
 
-Last, the user task that uses the sensor has to be created.
+Finally, a user task that uses the sensor has to be created.
 
 ```
 xTaskCreate(user_task, "user_task", 256, NULL, 2, 0);
 ```
 
+**Please note:** To avoid concurrency situations when driver functions are used to access the sensor, for example to read data, the user task must not be created until the sensor configuration is completed.
+
 The user task can use different approaches to fetch new data. Either new data are fetched periodically or the interrupt signal *nINT* is used when new data are available or eCO2 value exceeds defined thresholds.
 
 If new data are fetched **periodically** the implementation of the user task is quite simply and could look like following.
@@ -564,6 +566,8 @@ void user_init(void)
         // start periodic measurement with one measurement per second
         ccs811_set_mode (sensor, ccs811_mode_1s);
     }
+    else
+        printf("Could not initialize CCS811 sensor\n");
 }
 
 ```
diff --git a/extras/ccs811/ccs811.c b/extras/ccs811/ccs811.c
index 2087b2a..5bf60d8 100644
--- a/extras/ccs811/ccs811.c
+++ b/extras/ccs811/ccs811.c
@@ -494,7 +494,8 @@ static bool ccs811_reg_read(ccs811_sensor_t* dev, uint8_t reg, uint8_t *data, ui
     }
 
 #   ifdef CCS811_DEBUG_LEVEL_2
-    printf("CCS811 %s: Read following bytes: ", __FUNCTION__);
+    printf("CCS811 %s: bus %d, addr %02x - Read following bytes: ", 
+           __FUNCTION__, dev->bus, dev->addr);
     printf("%0x: ", reg);
     for (int i=0; i < len; i++)
         printf("%0x ", data[i]);
@@ -514,7 +515,8 @@ static bool ccs811_reg_write(ccs811_sensor_t* dev, uint8_t reg, uint8_t *data, u
 #   ifdef CCS811_DEBUG_LEVEL_2
     if (data && len)
     {
-        printf("CCS811 %s: Write following bytes starting at reg addr %02x: ", __FUNCTION__, reg);
+        printf("CCS811 %s: bus %d, addr %02x - Write following bytes: ", 
+               __FUNCTION__, dev->bus, dev->addr);
         for (int i=0; i < len; i++)
             printf("%02x ", data[i]);
         printf("\n");