為什么用電風扇降溫可能是危險的?

為什么用電風扇降溫可能是危險的?

Well, this blows.

好吧，這就是打擊。

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

一項新的研究發(fā)現(xiàn)，在極端高溫下使用電扇降溫只有在濕度較高的時候才有效。

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.

根據(jù)發(fā)表在《內(nèi)科醫(yī)學年鑒》上的一項研究，當濕度非常低時，風扇實際上會讓你感覺更熱，還會通過提高核心溫度讓你的心臟感到緊張。

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

研究人員提醒公眾，目前使用電風扇的指導方針是基于熱量指數(shù)，而不是實際溫度。

“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.

資深研究作者奧利·杰伊告訴路透社：“熱量指數(shù)(hi)這樣的綜合值，不適合作為是否使用風扇的參考標準。”

“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.

“在非常炎熱、干燥的條件下，HI相對較低，風扇是有害的;但在炎熱潮濕的環(huán)境中，HI相對較高時，風扇是有益的。”澳大利亞悉尼大學熱工效學實驗室主任杰伊補充說。

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.”

杰伊說，在非常炎熱干旱的條件下，“心臟必須做額外的工作來維持血壓，因為當一個人變熱時，血液被轉(zhuǎn)移到皮膚上，為促進冷卻，心臟必須加快跳動。”

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

他補充說:“(對身體)另一種形式的緊張是脫水，這也會導致體溫升高和心血管緊張。”

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.

在這項研究中，研究人員招募了12名沒有服用任何藥物、沒有任何醫(yī)療條件的男性，讓他們坐在一個模擬非常炎熱、干燥或炎熱、潮濕條件的氣候室中。

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

盡管濕度條件下溫度較低，但濕潤試驗的熱量指數(shù)仍高于干旱區(qū)的實驗指數(shù)。

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.

研究人員用三鉛心電圖和血壓測量了這些人的體溫，并評估了他們的心臟張力，最后通過追蹤汗液來測量脫水程度。

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.

風扇在潮濕的環(huán)境下使用(溫度為104華氏度，濕度為50%，HI為132.8)可以降低核心溫度和心血管壓力，同時提高舒適度。

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.

與此同時，在干旱條件下(溫度為116.6度，濕度為10%，HI為114.8)，風扇的使用提高了核心溫度和心血管壓力，讓男性感覺更熱——盡管HI比潮濕條件下要低。

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

雖然研究人員在研究中使用了臺座風扇，但“原理和吊扇是一樣的，”杰伊說。

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

約翰·霍普金斯醫(yī)學院急診醫(yī)學副教授馬修·利維博士說，這項新研究“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.

“有一些重要的收獲：在炎熱潮濕的環(huán)境中，人們用風扇的效果更好。在不可能有空調(diào)的情況下，這意味著人們有風扇總比什么都沒有好。”他告訴路透社。

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

利維說，這是因為風扇可以通過汗液的蒸發(fā)來幫助散熱。

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

“但是在干燥的環(huán)境中，風扇只會把更多的熱空氣推向你。”他補充說。