You’d surely think twice about ordering your favorite sub if you knew the deli’s meat slicer was a health hazard.

A recent report from the Centers for Disease Control and Prevention shows that many deli slicers are just that. In a survey that includes responses from nearly 300 delis, workers at almost half of the establishments admitted to C-D-C researchers that their meat slicers are not cleaned in keeping with the U.S. Food and Drug Administration’s recommended safety precautions.

The guidelines call for a full cleaning of slicers every four hours to help prevent bacteria growth and transfer. Fully cleaning a deli slicer requires disassembling and sanitizing the parts. It’s also essential to look for seals and gaskets on the machine that may be cracked or broken, allowing food and liquid to build up in places that are hard to reach or to see.

The survey results show that small and independently owned delis are less likely to comply with recommended cleaning practices. Delis with written cleaning protocols, those with workers trained in food safety and those that are part of a chain tend to adhere better to F-D-A cleaning standards, the C-D-C report revealed. A greater number of slicers in a deli also corresponded with greater frequency of full cleanings.

According to the C-D-C, going longer than four hours between thorough cleanings can lead to a buildup of listeria. This bacterium, which is common in delis and also spreads through other types of food establishments, regularly causes outbreaks of illness. So, the next time you stroll into your go-to sandwich shop, perhaps a quick quiz about the deli safety procedures should be part of your order.