首先要看塑料袋的外观是否有“食品用”的标志。通常这个标志应该在包装袋正面，比较醒目的位置。

Firstly, it is necessary to check whether the appearance of the plastic bag has a "food use" logo. Usually, this logo should be prominently placed on the front of the packaging bag.

其次是看颜色，一般而言，有颜色的塑料袋大都使用了废旧塑料的回收料，是不能用来装食品的。比如，一些菜市场用来装鱼、虾等水产品或肉类的劣质黑色塑料袋，或者是原本是用来装垃圾的塑料袋，消费者都应避免使用。

Secondly, it depends on the color. Generally speaking, plastic bags with colors mostly use recycled materials from waste plastics and cannot be used to hold food. For example, some markets use inferior black plastic bags to hold fish, shrimp, and other aquatic products or meat, or plastic bags that were originally used to hold garbage, consumers should avoid using them.

要看塑料袋有无杂质。将塑料袋放在阳光或灯光下，看是否有黑点，有没有口子。有杂质的塑料袋，肯定是使用了废塑料做原料。

Check if there are any impurities in the plastic bag. Place the plastic bag in sunlight or light to see if there are any black spots or gaps. Plastic bags with impurities must have used waste plastic as raw material.

闻一闻塑料袋有没有味道，是否让人觉得恶心。合格的塑料袋应该是没有味道的，而不合格的塑料袋由于使用了添加剂，会带有各种味道。

Smell if the plastic bag has any odor and if it makes people feel nauseous. Qualified plastic bags should have no odor, while unqualified plastic bags may have various odors due to the use of additives.

合格的塑料袋具有相应强度，不会一撕就破；而不合格的塑料袋由于添加了杂质，往往强度很差，容易破裂。

Qualified plastic bags have corresponding strength and will not tear easily; However, unqualified plastic bags often have poor strength and are prone to breakage due to the addition of impurities.

合格的塑料袋在抖动时，会发出清脆的声响；不合格的塑料袋往往是“嗡嗡”的闷响。

Qualified plastic bags will make a crisp sound when shaken; Unqualified plastic bags often have a buzzing sound.

把塑料袋放在水里，并用手将其按到水底，稍等片刻，浮出水面的即为不合格塑料袋，沉在水底的即为有毒塑料袋。

Put the plastic bag in the water and press it down to the bottom with your hand. Wait for a moment. The plastic bag that rises to the surface is considered unqualified, while the one that sinks to the bottom is considered toxic.

用手抚摸塑料袋表面，表面应该是光滑的。如果颜色混朦，触之发粘、发涩，就是有毒的。

Touch the surface of the plastic bag with your hand, and the surface should be smooth. If the color is blurry, sticky and astringent when touched, it is toxic.

燃烧：将塑料袋剪下一角，放在火上一烧，合格的烧之即燃，将它离开火后仍继续燃烧，并出现黄色火焰，而且熔塑像蜡烛一样一滴一滴往下掉，发出石蜡气味；有毒的，不易燃烧，燃烧后呈绿色火苗，并有一股呛鼻的异味。

Burning: Cut off a corner of the plastic bag and place it on the fire. Once it is qualified, it will ignite. After leaving the fire, it will continue to burn and a yellow flame will appear. The molten plastic will drop down like a candle, emitting a smell of paraffin; Toxic, not easily flammable, it turns into a green flame after combustion, and has a pungent odor.

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