All barcode types require a certain amount of light space (or quiet zone) to the left and right of the code. This enables the scanner to differentiate between the barcode and surrounding graphics. Should the wrong type of graphic image or colour intrude on the light margin, there is a risk that the barcode will not decode, or worse, will decode incorrectly.
One of the most common causes of bad reads is light margin incursion. For this reason, some symbologies employ a method of protecting the quiet zone. For example, an unbroken rule or box may be defined around the code. With the EAN-13 barcode, a human readable character appears to the left of the code but not on the right. In some countries, a recent change to the EAN-13 symbol specifications now recommends that a Light Margin Indicator (>) be placed on the right of the code, in the human readable field, with the tip aligned with the outer edge of the light margin to dissuade designers from placing graphics within the quiet zone.
Minimum Light Margins (EAN-13):
|Left Light Margin
|Right Light Margin
Also refer A - EAN-13.