Shulchan Arukh, Orach Chayim 433/שולחן ערוך·אורח חיים תל״ג

1Laws of Checking for Chametz. Containing 11 paragraphs: The checking should be done by candlelight, not moonlight. If one did not check on the night of the 14th, when checking during the day of the 14th, one should not check by sunlight but by candlelight. However, for a room with bright light, if one checked by sunlight it suffices, and the same applies to checking opposite a chimney in a room.

2One should not check by a torch's light but by candlelight. Not with a tallow, fat, or oil candle, but with a wax candle. (Rema: This applies to a single candle, but if there are two candles together, even braided ones, their status is like a torch) (The Maharil in the name of the Agudah).

3One checks all places where there may be a concern that chametz was brought in, therefore all rooms of the house and attics require checking, for sometimes a person enters with bread in hand. But wine cellars where bread is not suspected, as well as barns and the like, do not require checking.

4House holes and protruding beams from the walls that are not too high or low require checking. But very high ones beyond a person's reach, and low ones less than three handbreadths, do not require checking.

5The slanted roofs of an attic or tower, being unsuitable for any use, do not require checking even if inside the house.

6A cattle shed does not require checking, for if there was chametz there the animals would eat it. Similarly, a chicken coop does not require checking as the chickens would eat any chametz there. And the middle of a courtyard does not require checking, for if there was chametz there the ravens and other birds found there would eat it. This applies to possible chametz, but for definite chametz, it does. Rema: But in Siman 445:3 it is clarified that it is permitted to discard chametz where birds frequent, certainly not needing to remove even definite chametz from there before its prohibition time.

7For a hole between one Jew's home and another's, each checks as far as their hand can reach, and the rest is nullified mentally, which suffices. But for a hole between a Jew and a non-Jew, no checking at all is required lest the non-Jew say "He is working sorcery against me" and this leads to danger.

8If a wall was used with chametz in its holes, and it collapsed forming a mound, even if less than three handbreadths high enough for a dog to dig, one need not check underneath it. Since scorpions frequent such mounds, we are concerned that after finishing the required checking, no longer engaged in a mitzvah, one may search there for a lost needle and endanger oneself. This applies generally, but if it is known there is chametz under a mound less than three handbreadths high, it must be removed carefully without danger. If over three handbreadths high, it is nullified mentally, which suffices.

9In a wine cellar where rows of barrels are arranged one next to the other until it is filled, and more rows are then arranged on top of the lower ones up to the ceiling beam, one only needs to check the top row and one below it, meaning the row across the width of the cellar, not the entire area, but the top visible from the beam and entrance, and one below it.

10Synagogues and study halls require checking, for children usually bring chametz inside.

11One who cleans their room on the 13th of Nissan intending to check for and burn the chametz, being careful not to bring more chametz in, must still check on the night of the 14th. Rema: Everyone must clean their rooms before checking (Mordechai at start of Pesachim). Pockets or sleeves of clothes where chametz may sometimes be kept require checking (Mahari Weil).