What item is typically prohibited from being brought through security checks?

The prohibition of liquids over 100ml in a container during security checks is rooted in safety regulations aimed at preventing the transport of potentially hazardous substances. This rule originated from heightened security concerns regarding liquid explosives. By limiting the size of liquid containers, security personnel can more effectively screen carry-on items and reduce risks during flights. Allowing containers that exceed this volume could pose a significant threat that security systems cannot adequately assess in a timely manner, thus leading to stringent restrictions on liquids.

In contrast, items such as laptops in protective cases, small electronics like headphones, and coats and jackets are permissible because they are not considered security threats when processed through screening. Such items can typically be subjected to additional screening if necessary but do not fall under the prohibitive regulations that apply to larger liquid containers.