Optimally, get one with a HEPA “completely sealed” system.

最好带有HEPA（高效空气过滤器）“完全密封”系统。

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If you are locked in a completely sealed room, you will die of carbon dioxide poisoning first before you will die of oxygen deprivation.

如果你被关在一个完全密封的房间内，你会先因二氧化碳中毒而死亡，而不会先因缺氧而死亡。

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Make sure the room has been completely sealed.

保证房间是完全密封的。

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It can fold in on itself to become a completely sealed concrete block, preventing any of the undead from getting in.

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But the well may not be completely sealed off until at least until August, when BP hopes to complete a relief well.

CNN: BP robots steer cap to spewing well

To dampen vibration (hard drives like these have platters that spin thousands of times per minute), the Blade Runner's case is heavy, solid and completely sealed.

WSJ: A Hard Drive With Quiet Style | Geek Chic