为什么用电风扇降温可能是危险的?

为什么用电风扇降温可能是危险的?

Well, this blows.

好吧，这就是打击。

A new study has found that using electric fans to cool down during extreme heat is only effective when the humidity is high.

一项新的研究发现，在极端高温下使用电扇降温只有在湿度较高的时候才有效。

When the humidity is very low, the fans can actually make you feel hotter — and can strain your heart by spiking core temperature, according to the study published in the Annals of Internal Medicine.

根据发表在《内科医学年鉴》上的一项研究，当湿度非常低时，风扇实际上会让你感觉更热，还会通过提高核心温度让你的心脏感到紧张。

The researchers warned that current guidelines for the use of electric fans is poorly based on heat index and not on the actual temperature.

研究人员提醒公众，目前使用电风扇的指导方针是基于热量指数，而不是实际温度。

“A combined value such as heat index (HI) is not appropriate for advising whether fans should be used or not,” senior study author Ollie Jay told Reuters.

资深研究作者奥利·杰伊告诉路透社：“热量指数(hi)这样的综合值，不适合作为是否使用风扇的参考标准。”

“In very hot, dry conditions the HI was relatively lower, yet fans were detrimental; but in hot-humid conditions the HI was relatively higher and fans were beneficial,” added Jay, director of the Thermal Ergonomics Laboratory at the University of Sydney in Australia.

“在非常炎热、干燥的条件下，HI相对较低，风扇是有害的;但在炎热潮湿的环境中，HI相对较高时，风扇是有益的。”澳大利亚悉尼大学热工效学实验室主任杰伊补充说。

Jay said that in the very hot-arid conditions, “the heart has to do extra work to maintain blood pressure because as one gets hot, blood is diverted to the skin to facilitate cooling and the heart must beat more times per minute.”

杰伊说，在非常炎热干旱的条件下，“心脏必须做额外的工作来维持血压，因为当一个人变热时，血液被转移到皮肤上，为促进冷却，心脏必须加快跳动。”

He added: “Another form of strain (on the body) is dehydration, which also contributes to increases in body temperature and cardiovascular strain.”

他补充说:“(对身体)另一种形式的紧张是脱水，这也会导致体温升高和心血管紧张。”

For the study, the researchers recruited 12 men who were not taking any medication and had no medical conditions to sit in a climatic chamber that simulated either very hot, dry conditions or hot, humid conditions.

在这项研究中，研究人员招募了12名没有服用任何药物、没有任何医疗条件的男性，让他们坐在一个模拟非常炎热、干燥或炎热、潮湿条件的气候室中。

The heat index for the humid tests was higher than for the arid ones even though the temperature was lower in the humid condition.

尽管湿度条件下温度较低，但湿润试验的热量指数仍高于干旱区的实验指数。

The researchers measured the men’s temperatures rectally and assessed their heart strain using three-lead electrocardiography and blood pressure. They measured dehydration by keeping track of sweat.

研究人员用三铅心电图和血压测量了这些人的体温，并评估了他们的心脏张力，最后通过追踪汗液来测量脱水程度。

Fan use in the humid conditions (temperature at 104 degrees Fahrenheit, humidity at 50 percent and HI at 132.8) reduced core temperature and cardiovascular strain while improving comfort.

风扇在潮湿的环境下使用(温度为104华氏度，湿度为50%，HI为132.8)可以降低核心温度和心血管压力，同时提高舒适度。

Meanwhile, in the arid conditions (temperature at 116.6 degrees, humidity at 10 percent and HI at 114.8) the fan use raised core temps and cardiovascular strain, and made the men feel hotter — even though the HI was lower than it was in the humid condition.

与此同时，在干旱条件下(温度为116.6度，湿度为10%，HI为114.8)，风扇的使用提高了核心温度和心血管压力，让男性感觉更热——尽管HI比潮湿条件下要低。

While the researchers used pedestal fans for the research, “the principles are the same for a ceiling fan,” Jay said.

虽然研究人员在研究中使用了台座风扇，但“原理和吊扇是一样的，”杰伊说。

The new study “is very interesting,” said Dr. Matthew Levy, an associate professor of emergency medicine at the Johns Hopkins School of Medicine.

约翰·霍普金斯医学院急诊医学副教授马修·利维博士说，这项新研究“非常有趣”。

“There are some significant takeaways: people in hot, humid conditions tend to do better with a fan. In situations where air conditioning is not possible, this means people would do better with a fan than nothing at all,” he told Reuters.

“有一些重要的收获：在炎热潮湿的环境中，人们用风扇的效果更好。在不可能有空调的情况下，这意味着人们有风扇总比什么都没有好。”他告诉路透社。

That’s because fans can help with heat loss through evaporation of sweat, Levy said.

利维说，这是因为风扇可以通过汗液的蒸发来帮助散热。

“But in a dry environment, the fans just push more warm air toward you,” he added.

“但是在干燥的环境中，风扇只会把更多的热空气推向你。”他补充说。