The answer first: the severity of piercing hall (穿堂煞) is not fixed — it depends on which palace that airflow axis runs through. If the axis crosses the palace holding the timely, wealth-bearing facing star, then yes, that is a real wealth-leaking layout and worth spending money on. If it crosses a palace that is already untimely, it is closer to "not ideal" than to "disaster" — put up one screen and move on to the next problem.
Estate agent articles and renovation blogs will only tell you "piercing hall is bad, build a foyer". That is not wrong, but it makes every piercing hall look equally serious, and so two kinds of people make bad decisions: one gutting and rebuilding an entire entryway over a layout with limited impact, and another going numb — "everyone says it's bad" — and doing nothing even about the genuinely serious kind.
What actually counts as piercing hall
Stand at the main door and look in. If directly opposite there is another opening to the outside in a straight line — a back door, a floor-to-ceiling window, a large window, a balcony door — that is piercing hall (穿堂煞, also called 穿心煞 or 一箭穿心, "an arrow through the heart").
The key phrase is "opening to the outside". Two things to note:
The classical explanation of this layout is that "qi comes straight in and straight out, and does not stay". Put plainly: for a space to gather qi, the qi has to circle, linger and circulate inside it. A straight through-passage lets qi in one end and out the other, and the home is energetically in a state of "not holding on to things" — which shows up in daily life as money arriving and leaving without accumulating.
Why severity varies so much
Xuan Kong Flying Stars divides a home into nine palaces (宮位), each holding two stars: the mountain star (山星) governs people and health, the facing star (向星) governs wealth and career. The "wealth position" is not some fixed compass direction — it is wherever the timely facing star has flown to, and it changes with the period (元運).
What piercing hall actually does is drain the qi from a specific palace. So the question is not "do I have piercing hall" but "which palace's qi is it draining":
The axis crosses the palace of the timely facing star → this is the worst case. The chart says this home has wealth, but the palace holding that wealth star is run through by a piercing axis — money comes in one end and leaves by the other. In this situation even a beautiful chart cannot hold wealth, and a screen or a foyer is a necessary investment rather than an optional one.
The axis crosses an untimely palace, or one holding an inauspicious star → far less impact. There is even a view that for certain inauspicious palaces, ventilation is not a bad thing. A token treatment here is enough — a half-height partition, a high-backed sofa turned to block the line — and there is no need to touch the structure.
The axis crosses the central palace (中宮) → the central palace is the core of the whole home, so this case also tends toward serious, because it affects the qi circulation of the entire dwelling rather than one function.
This is why, faced with the same "front door aligned with a floor-to-ceiling window", some practitioners say fix it immediately and others say it is fine — they are not looking at the same thing. The first is reading the chart; the second is reading the layout.
The check you can run yourself
Your phone is all you need:
Do those five steps and you already know whether you have piercing hall and where it runs. That is more than nine out of ten articles online will give you.
Where this self-check runs out
What you are missing is the last piece: which palace that line falls in on your home's chart, and whether that palace's facing star is timely or spent.
That piece cannot be judged by eye, because it depends on three things at once:
So the self-check can tell you "there is a piercing axis here, running through the living room", but it cannot tell you whether that is "this axis is draining the only prosperous wealth position in your home — treat it first" or "this axis has limited impact, deal with something else first". Those two conclusions lead to completely different budgets.
Common treatments, and their trade-offs
If you have confirmed it needs treating, from lightest to heaviest:
Two things not to do: do not hang a mirror on the axis (mirrors reflect the qi mouth and usually complicate matters); and do not buy religious or ritual merchandise to "suppress" it — the cause of this layout is a physical through-passage, and the treatment should be physical too.
In one line
Piercing hall is real, but "do I have it" and "how bad is it" are two separate questions. You can answer the first yourself; the second needs your home's actual Flying Stars chart, to see whose qi that axis is draining. Run the five steps above and you will at least know what you are dealing with.