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Thermos flask with cup – factors to consider for safe use

Thermos flask has been a popular item to keep our hot or cold drink. Manufacturers have stepped up in broadening user's convenience by turning the lid into a cup. If you have ever wondered if it was safe to drink from this lid, the answer rests with the material and design of the thermos flask with cup. Let’s find out more about it in this article.

Types of thermos flask having cup-like lid

These are several types of thermos flask with cup.

Initially the lid was only meant to cover the mouth of the thermos flask, preventing the penetration of dust, insects or in the case of water leakage. Then some users must have found that it was more convenient when they used the lid as a cup so they could enjoy their drinks everywhere.

Taking from there, manufacturers have invented new lids with special handles, double or triple layers, which could be separated into several cups, to add on their basic and classic lid collection.

Straight-shaped vacuum flasks like the portable individual flasks and classic-designed flasks often have cup-like lids. These types of flask come in various volumes, ranging from 0.45 liter to 3.2 liters. The larger the volume, the bigger the lid.

However, no matter the cup-like design, some lids should not be used as a cup due to several reasons, which are explained in the next part.

Key points in evaluating the safeness of the cup-like lid

A sample of the 3.2-liter thermos flask with cup from Rang Dong, Vietnam's leading manufacturer of vacuum flask products.

There are three factors to consider, namely the material, the size and the non-burn design before deciding to use a thermos flask’s lid as a cup.


The thermos flask must comply with health safety standards of the local market for food contact objects. The inner layer and the stopper of the flask are the parts directly contacting the drinks so if they meet the standard, so does the flask. The lid is not mentioned here because its original purpose is to cover the flask mouth and doesn’t contact the drink. Hence, even when a vacuum flask is stated ‘food grade’, it doesn’t mean to include its lid.

Therefore, consumers should learn to tell if a lid can be used as a cup by checking its material specification. If the lid is made of BPA-free material, usually PP for plastic, and 304 or 316 stainless steel, it is safe to use. These are the common materials for lids as well as the flask’s body thanks to their excellent thermal and chemical resistance.


The size of the lid is the next factor to consider. An individual thermos flask with cup has a small lid, similar to a cup, while big classic types of flasks, like the 3.2-liter thermos, have lids with the size of a bowl. Such a big size may not make the lid suitable to use for tea.

Non-burn design

The material of the lid is food grade and heat resistant, but it doesn’t mean users won’t get burned when using it. Besides, a stainless-steel lid even becomes hot quickly, so that it’s hard to hold it with bare hands. Therefore, lids designed with a handle are more suitable. Non-handle lid is for warm or cool drinks only.

Later, many manufacturers have invented the vacuum lid to protect customers from getting burned.

Should you have any questions or request a quotation of Rang Dong products, please send us an email to: export@rangdong.com.vn.

Websites: en.rangdong.com.vn and vacuumflask.rangdong.com.vn

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