The haze is back: Do you need an N95 mask? What about a surgical mask?

Here's a quick refresher to get you up to speed. And can you use your old stash of N95 masks?

Can you still remember what to do when the haze worsens? (Photo: iStock/Panuwat Dangsungnoen)

Well, the haze is back. And in full force. But does that mean you need to reach for an N95 mask whenever you head outdoors? And will the surgical or fabric masks you used during the COVID-19 pandemic offer enough protection? Here's what you need to know.

WHAT EXACTLY ARE WE TRYING TO FILTER OUT?

During the haze, the particles in the air tend to consist of a high concentration of coarse and fine particles from large-scale forest and land fires, said Adjunct Associate Professor Adrian Kee, the head and a senior consultant at National University Hospital’s Division of Respiratory & Critical Care Medicine.

“Coarse particles usually flush out of the atmosphere within a day, while fine particles are able to stay in the atmosphere and travel extensive distances of hundreds to thousands of kilometres,” he said. “The haze we experience contains particulate matter less than 10 micrometres in size, including fine particles of less than 2.5 micrometres.”

And these fine particles are what’s causing respiratory issues such as coughing and difficulty in breathing as well as worsening existing respiratory conditions such as asthma. “Haze particles can also cause irritation to the eyes, throat and nose, among other negative health effects,” said Adj Assoc Prof Kee.

An N95 mask can filter out fine particles that are about 0.1 micrometres to 0.3 micrometres in size, he said. “Studies show that they are at least 95 per cent effective with proper fit and usage.”

However, the key words here are “proper fit”. “An N95 mask is only effective if the mask is properly sized and fitted for the individual. It should also not be soiled, distorted or damaged,” said Dr Esther Pang Pee Hwee, a senior consultant with Tan Tock Seng Hospital’s Department of Respiratory and Critical Care Medicine.

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IF I’M HEALTHY, DO I STILL NEED AN N95 MASK WHEN I'M OUTSIDE?

N95 masks aren’t needed if you’re commuting from home to school or work, said Adj Assoc Prof Kee. But when the air quality is unhealthy (PSI 101 to 200), those with chronic lung or heart disease should avoid prolonged or strenuous outdoor physical exertion, he said. The same applies to older adults, pregnant women as well as children.

If you have to be outside when the 24-hour PSI is in the hazardous range, that is, higher than 300, consider wearing an N95 mask, said Dr Pang. “Short-term exposure to such high levels of air pollutants may cause irritation of the eyes, nose and throat in healthy individuals.”

An N95 mask can filter out fine particles that are about 0.1 to 0.3 micrometres in size. (Photo: iStock/Anucha Ruenin)

WHAT ABOUT PEOPLE WHO ARE MORE VULNERABLE TO THE HAZE?

If the air quality reaches PSI 201 to 300 (very unhealthy), those with chronic lung or heart disease should avoid outdoor activities, while older adults, pregnant women and children should minimise outdoor activities, said Adj Assoc Prof Kee.

There is “currently no approved certification standard for masks” for children, said Dr Pang, so “the best form of protection for them is to stay indoors” when the 24-hour PSI reaches hazardous levels or the 1-hour PM2.5 reading reaches high levels.

CAN I USE THE SURGICAL AND FABRIC MASKS I WORE DURING THE PANDEMIC?

Surgical and fabric masks don't offer the same protection from fine haze particles as an N95. You can breathe better in a regular mask but you’re only filtering out larger irritant particles in the air, according to Adj Assoc Prof Kee. “They are not effective in filtering fine particles that are 2.5 micrometres or less in size present in haze.”

Moreover, the regular masks “typically have a looser fit and can allow fine particles to enter around the edges”, he said.

HOW DO I KNOW IF MY STOCKPILE OF N95 MASKS IS STILL USABLE?

“Check the expiration date indicated on the packaging,” said Dr Pang. “You should not use masks past their expiration date. The effectiveness of the masks may degrade with time.”

Also, look for visible defects such as shape deformities or tears. “The elastic bands should have good elasticity without snapping easily. The metal nose bridge should be in good condition. These are important for achieving a good mask seal,” said Dr Pang.

Next, do a fit check by placing the N95 mask on your face. “Feel for air leakage from the edges of the mask while breathing in and out,” she said.

“If you are still unsure of your N95 mask’s condition, consider consulting with your doctor or nurse. They can assess the masks and advise on their usability.”

WHAT IF I HAVE RESPIRATORY ISSUES AND FIND IT HARD TO BREATHE WITH THE N95 MASK?

Check with your doctor for personalised advice on whether you should wear an N95 mask if you have difficulty breathing at rest or on exertion, said Adj Assoc Prof Kee. The same thing applies if you’re an older adult, pregnant or suffer from severe lung or heart problems.

Other than that, your best alternative is to stay indoors during periods of very unhealthy or hazardous air quality, said Dr Pang.

“If you need to be outdoors, avoid strenuous activities or minimise the duration of the outdoor activity,” she said. “Continue with the treatment prescribed for your respiratory condition. If you still feel unwell or develop respiratory symptoms, you should seek medical attention promptly.”

But rather than risk it, it’s best to stay indoors and limit outdoor activities until the haze situation improves, said Adj Assoc Prof Kee.

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这里快速回顾一下，帮你快速掌握要点。你还能用之前囤的N95口罩吗？

你还记得雾霾加剧时该怎么做吗？（图片：iStock/Panuwat Dangsungnoen）

雾霾又回来了，而且来势汹汹。但这是否意味着你每次出门都需要戴N95口罩呢？你在新冠疫情期间使用的医用口罩或布口罩是否能提供足够的防护？以下是你需要了解的信息。

我们究竟想要过滤掉什么？

新加坡国立大学医院呼吸与重症监护医学科主任兼高级顾问、兼职副教授 Adrian Kee 表示，雾霾期间，空气中的颗粒物往往由大规模森林和土地火灾产生的高浓度粗颗粒物和细颗粒物组成。

他说：“粗颗粒物通常会在一天之内从大气中消散，而细颗粒物则能够在大气中停留更长时间，并传播数百至数千公里。我们所经历的雾霾中含有小于10微米的颗粒物，其中包括小于2.5微米的细颗粒物。”

这些细小的颗粒物正是导致咳嗽、呼吸困难等呼吸系统问题以及加重哮喘等现有呼吸系统疾病的罪魁祸首。“雾霾颗粒还会刺激眼睛、喉咙和鼻子，并造成其他一系列负面的健康影响，”副教授基说道。

他说，N95口罩可以过滤掉尺寸约为0.1微米至0.3微米的细小颗粒。“研究表明，如果佩戴和使用得当，它们的过滤效果至少可达95%。”

然而，关键在于“合适的尺寸”。陈笃生医院呼吸与重症监护医学科高级顾问彭佩慧医生表示：“N95口罩只有在尺寸合适、佩戴贴合个人面部的情况下才能有效。此外，口罩不应被弄脏、变形或损坏。”

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如果我身体健康，外出时还需要戴N95口罩吗？

Kee副教授表示，如果只是从家通勤到学校或工作地点，则无需佩戴N95口罩。但他指出，当空气质量不佳（PSI值在101至200之间）时，患有慢性肺病或心脏病的人应避免长时间或剧烈的户外体力活动。老年人、孕妇和儿童也应如此。

庞医生说，如果24小时空气污染指数（PSI）高于300（即处于危险范围），而你必须待在户外，那么请考虑佩戴N95口罩。“即使是健康人，短期暴露在如此高浓度的空气污染物中也可能导致眼睛、鼻子和喉咙受到刺激。”

N95口罩可以过滤掉尺寸约为0.1至0.3微米的细小颗粒。（图片：iStock/Anucha Ruenin）

那么，那些更容易受到雾霾影响的人群该怎么办？

副教授基表示，如果空气质量达到 PSI 201 至 300（非常不健康），患有慢性肺病或心脏病的人应避免户外活动，而老年人、孕妇和儿童应尽量减少户外活动。

庞医生表示，目前“儿童口罩尚无认可的认证标准”，因此，当 24 小时 PSI 值达到危险水平或 1 小时 PM2.5 读数达到高水平时，“对他们来说最好的保护方式是待在室内”。

我可以使用疫情期间佩戴过的医用口罩和布口罩吗？

外科口罩和布口罩对雾霾中细小颗粒的防护效果不如N95口罩。据副教授Kee称，普通口罩虽然透气性更好，但只能过滤掉空气中较大的刺激性颗粒。“它们无法有效过滤雾霾中存在的2.5微米或更小的细小颗粒。”

此外，他还表示，普通口罩“通常贴合度较差，细小颗粒可能会从边缘进入”。

如何判断我囤积的N95口罩是否还能使用？

庞医生说：“请查看包装上标明的有效期。不要使用超过有效期的口罩。口罩的防护效果会随着时间推移而降低。”

此外，还要检查是否有明显的缺陷，例如形状变形或撕裂。“松紧带应该弹性良好，不易断裂。金属鼻梁条也应该完好无损。这些对于确保口罩密封性至关重要。”庞医生说道。

接下来，将N95口罩戴在脸上进行贴合性检查。“吸气和呼气时，感受一下口罩边缘是否有漏气，”她说。

“如果您仍然不确定您的N95口罩状况如何，请考虑咨询您的医生或护士。他们可以评估口罩并就其是否仍然可用提供建议。”

如果我有呼吸系统疾病，戴上N95口罩后呼吸困难怎么办？

Kee副教授表示，如果您在休息或运动时呼吸困难，请咨询医生以获得关于是否应该佩戴N95口罩的个性化建议。如果您是老年人、孕妇或患有严重的肺部或心脏疾病，也应如此。

庞医生说，除此之外，最好的办法就是在空气质量非常不健康或有害的时候待在室内。

“如果必须外出，请避免剧烈运动或尽量缩短户外活动时间，”她说道。“继续接受针对您呼吸系统疾病的治疗。如果您仍然感觉不适或出现呼吸道症状，应立即就医。”

副教授基表示，与其冒险，不如待在室内，限制户外活动，直到雾霾情况好转。

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