I arrived in San Francisco on a Wednesday.

From one end of the Golden Gate Bridge I couldn't see the other. Not because of the famous fog. Because of the smoke. The Camp Fire had already been burning uncontrolled for almost a week, and the wind had aimed its 145,000 acres of death and destruction-laced smoke directly at the city.

Some of my friends - the nervous, the rich, the pregnant - fled the city. Others stayed, and prayed that things would get better. They didn't.

By Friday the smoke had gotten worse. A lot worse. On the map, Bernal Heights went from red to purple. That was worse than Beijing, if better than Delhi, where the poor were burning tires in the streets to stay alive. But this was San Francisco, the heart of the technology boom, one of the richest cities in the world, and a city of privilege unaccustomed to realities that hundreds of millions of people unavoidably have to live with every day.

Venturing out of the my Airbnb without a mask felt like an act of foolhardy courage. The streets were deserted, and the few people out were either bums or wearing heavy-duty masks.

Trust San Francisco to illustrate the consequences of class so dramatically. The bums breathed the particulate-filled air directly. Most people had to make do with surgical masks and crossed their fingers that the dirty air didn't seep around the rough fabric's edges. Then there were the people I saw in Cow Hollow and Pacific Heights with full fledged respirators, dual-HEPA filters included. The Matthew principle in action.

The smoke hung so heavy that buildings even a few blocks away were Impressionist. Any further, and they simply vanished. I could taste the air. Some part of me could already feel the particulates gathering in my lungs, but I chalked this up either to hypochondria or psychosomatic belief.

It's strange, being in a city where everyone has either hunkered down inside or already fled. City streets don't look right without people. In the country, emptiness is refreshing, natural. In the city, it's a constant siren reminding you that something is seriously wrong.

I remembered walking home from my Midtown office building after the World Trade Center came down. I remembered how Santa Barbara had felt, less than a year earlier, as ash drifted down from the Thomas Fire to coat my black Camry gray. I remembered walked to my East Village apartment through blacked-out streets in the aftermath of Hurricane Sandy. Walking in the Mission that Friday felt similar.

It wasn't just that the streets were creepily empty, or that people weren't talking. Most of the shops were closed. Schools were closed. The cable cars weren't running. Traffic was disturbingly sparse. Even though I knew the reason why, part of me wondered if some general alert hadn't been broadcast, some urgent warning of greater danger that I'd missed. In a strange way, I felt like I was living in an occupied city.

The pervading sense of unease was like a toothache. I couldn't fight. I couldn't flee. I couldn't solve the problem. I had to grin and bear it. Basic plans and routines were insufficient. Walking around was right out. Simple errands required forethought and planning. And all the while, in the back of my mind, that never-ending wonder if I was doing the right thing by staying.

It was impossible to figure out the health impact of the smoke. There were no studies, no data. Some estimated it was like smoking 5 cigarettes a day; others, half a pack. But if on one side there were guesstimates and denial, on the other side was fear. Every time I breathed in, I wondered if my breath was tightening, if some random pain was indicative of far worse to come. And then I ridiculed my fear as being the symptom of a too-safe, too-easy life. I mocked San Francisco for shutting down over an air quality that was the standard of life over much of Asia. And then, on the next inhale, the fear returned. I would try to calculate how long I'd been outside, how far to my next stop, how soon before I could get back inside.

By the time I got home, my clothes smelled like I'd spent the day at a bar. A bar, that is, before Bloomberg's smoking ban spread across the country. It's a dreadful smell, clothes drenched with smoke and sweat. The apartment didn't have a washer, or I scrubbed them in the sink with hand soap, wrung them out, and hung them up on the shower rod to dry.

The next day, Saturday, I stayed inside. The city had shrunk to ten blocks in any direction. Even the massive skyscrapers of the Financial District were gone. Without daring even to open the door to the balcony, I suffered bouts of claustrophobia. My heart rate would accelerate uncontrollably and I would curse myself for not renting a car and driving south as soon as I entered this forsaken city.

All my usual pastimes lost their flavor. I found it impossible to concentrate on reading, or music, even Netflix. Too much of my brain was uselessly whirring, trying to understand an unsolvable problem and refusing to accept the simple fact that doing nothing was the optimal - and only - strategy.

I found myself wondering how Preppers ever imagined that they could live underground in their homemade bunkers for months on end and keep their sanity. Americans simply aren't used to living even for a single day without the Internet, without fresh food, without the electricity grid, without the ability to step outside. All those cans of tuna fish and MRE kits would be useless, faced with the madness that would descend. They'd scratch their nails bloody on the walls or stab each other to death just to get a reprieve from the unrelenting boredom and the mounting pressure of the too-close walls.

My mom called me that evening, full of concern. Did I know how bad the air was? Did I realize that I was threatening - perhaps permanently - my lung function? Did I get how particulates could lodge in my lungs and stay there forever? A couple clickbait articles combined with CNN hysteria and now my mom was an expert. Not that I knew any more than she did; I didn't. But I very aware of my own ignorance.

When she told me I should flee the city, take a flight to wherever for a couple days, I understood her fear. But I wasn't going to leave, and said as much. Why not? Leaving seemed pointless. I was spending very little time outdoors and even that, apparently, was no worse than smoking a couple of cigarettes a day.

I understood that I couldn't know exactly how much harm I was doing to myself, but I reasoned - perhaps starting with the conclusion that I didn't want to bother schlepping out of state - that we all live in a constant state of uncertainty. We all run risks we don't understand and cannot measure. Risk is inevitable. Danger is unavoidable.

Should I never drive to the grocery store, because I could get T-boned by a drunk? Should I never take a shower, because I could slip and fall in the tub? Should I never walk by myself, because I could get mugged or murdered? What about the risk from my diet? From drinking tap water? From riding the subway?

In a world where safety is impossible, we're forced to run innumerable, albeit unlikely, risks every day. And attempts to stay safe simply make us weak. If I fled this danger, the next danger would loom larger. I would have trained myself that fear and flight were the correct approach to uncertainty. Action of any kind would become more difficult, look more frightening, appear more dangerous. Inch by inch, the fearful build their own prisons and are still afraid.

Not that I was a determinist, or blase about my own safety. I had simply done the analysis to the best of my - admittedly poor - ability, and decided that the risk of staying was low enough not to warrant packing, getting a Lyft to the airport, dealing with SFO, flying to Boise or Phoenix or Las Vegas, getting a hotel room, waiting an indeterminate number of days, getting the all clear, and then reversing the process.

I reminded my mom how, where she lives, a foot of snow is normal. No one flies, terrified, to Miami. Yet bad weather costs lives. Road collisions increase. The elderly run a higher risk of dying in their homes, or having an accident. Now, some cities shut down over two inches of snow. It's a question of what you're used to. We accept that risks have to be run. Where we draw the line of what risk is unacceptable… well, that's different for each of us.

When I was living in the East Village and Hurricane Sandy struck, I made the decision to get the heck out of my powerless apartment in about twenty minutes. I had returned from a business trip on Thursday and assumed, after four days of repairs, that surely the power was back on. It was, above 34th street. At 10th and First, not so much.

In my hubris, I assumed staying in my apartment through a blackout would be no big deal. Then I tried it. Some of my friends did tough it out; I can't imagine how depressing those days were for them. My refrigerator, even after being emptied, stank. The whole street stank as the garbage rotted. I couldn't take a shower. I couldn't cook. Little light penetrated my apartment. Definitely not enough to read. I had no candles. No canned food. No crank radio. All the little electronic amusements that I had taken for granted now loomed as enormous necessities. My phone? Unchargeable. Dead. My laptop? Unchargeable. Dead. The Internet. Down. I sat in the twilight for twenty minutes, unable to do anything at all, feeling more and more gloomy, then bailed.

I walked north, away from the grim disintegration of lower Manhattan. Crossing 34th Street was crossing from the darkness into the light. Below that line, people scrounged and scuttled without talking or making eye contact. Above that line, life went on. And not just any life. The incredibly rare, privileged life of Western civilization that I took for granted, with running water and electricity and working refrigerators and stores that were open.

At 57th Street, I stopped at a hotel and called a friend, who graciously invited me to crash with him on 88th Street. Each afternoon for the next three days I walked the four miles south to see if the lights were on yet; each time they were not. Each time it felt like walking into the non-functional, deserted chaos of a post-apocalyptic city.

Remembering those days reminded me that I wasn't dogmatic about staying in a stupid situation. If things got bad enough, I would bail. Mentally, I pre-committed to leaving if the air quality index rose to the 400s. Again, that would have been just another day in Delhi, but San Francisco would probably have gone to DEFCON 1.

After talking with my mom, I started to itch with cabin fever. I resolved to venture outside on Sunday. At the very least, I needed groceries. I felt like a man preparing for a retrieval mission behind enemy lines. Keep your head down. Move directly point to point. Anticipate. Again, some part of me realised how ridiculous I was being, how soft I was to think that this was anything like real hardship, how pathetic I'd become to lose myself to fear so easily. And some part of me told that other part of me to go fuck itself. It is so easy to scoff at the most dreadful suffering when you are safe with a full stomach.

Sunday morning I went to one of the YMCA branches in the city and groaned as my Lyft pulled into an empty parking lot. Closed. I cursed my own stupidity, for trusting Google and not going to the source, for not checking the YMCA's own webpage. I stewed in that anger as I walked over to a coffee shop. I missed coffee. The air tasted clearer, but I knew I knew nothing. Completely ignorant, my imagination took the reins, conjuring one awful scenario after the next.

There were more people out on the streets, but most of them were still wearing masks. The masks, and what they implied, added color to my fears. I felt pressured to conform. What did they know that I did not? It was easy, from a distance, to dismiss their worries as paranoia, the overreactions of a coddled elite, but up close I felt like the sucker, the idiot who didn't realize the damage that was being done to his lungs in real time.

Sitting in the coffee shop, however, sipping my too-hot coffee, watching the line move, was therapeutic. Reassuring. Masks or not, life continued. Normal daily routines continued. People were going about their lives, without panic or anxiety. The city, after being drained of energy, was filling back up.

Later, I went to a different branch of the Y, one that had remained open. Two old men were busy explaining to each other what the forestry service had gotten wrong, and how to solve the problem. I wanted to laugh at them, laugh at their arrogance. Then I remembered how I had believed that I, too, had figured out a solution to this enormously difficult and complex problem in thirty seconds. A problem that hundreds of smart, dedicated people were working on without success. It felt better to think that an easy answer existed. The truth was far scarier: the world was complex and unpredictable and uncontrollable. I empathized with them; even the illusion of certainty was comforting, while the reality of helplessness and lack of control was unsettling.

One of the old men went around and talked briefly with several of the people who were changing in the locker room. He seemed desperate to talk, desperate to tell people that he was 87 years old and that his friends were dying all around him. One moment he would be discussing his approaching death matter-of-factly, almost thankfully, describing the societal horrors that would inevitably befall us "youngsters" after he was safely in the grave. The next moment he would dispense advice on how to stay young and healthy, mocking those who hadn't. His advice was quite good: stay active, stay busy, stay involved, stay connected. Still, the men he cornered, myself included, looked at him with bewilderment, ummed and ahhed politely, and accelerated their movements. Honesty from strangers can be awkward enough; receiving that honesty while button-holed and naked doesn't help.

I adjusted to the new normal. And then, a couple of days later, rain fell. That was the end of the smoke. The air quality turned green. And people returned to their daily affairs. The memory of a city is short.