HVAC - Electromechanical Installation of Underground Civil Air Defense Works (I)

2026-06-08

I. General Requirements for Embedded Works in Civil Air Defense Zones

Scope of embedded works: Embedded conduits and sleeves for all disciplines within civil air defense zones.
Several standby pipes shall be pre-embedded in the frame walls of airtight blast doors and airtight doors at all personnel access openings and connecting openings for peacetime use. Hot-dip galvanized steel pipes with a nominal diameter of 65 mm and a wall thickness of no less than 2.5 mm shall be adopted.
All cable conduits penetrating exterior walls, free-standing walls, blast-proof partition walls and airtight partition walls shall be pre-embedded with standby pipes, and corresponding blast-proof airtight or airtight treatment shall be implemented.
One circuit of low-voltage cable shall be routed from the basement power distribution room to each distribution box in civil air defense zones. The civil air defense power supply from the wartime regional power station on adjacent plots shall serve as the wartime standby power supply. Commissioning of the wartime power supply shall be completed within the 3-day conversion period upon the outbreak of war. Embedded conduits for power circuits shall be installed during peacetime.
Reserved openings for installation of various equipment.

II. Notes on Civil Air Defense Construction

All pressure pipelines penetrating blast-proof partition walls, airtight partition walls and roof slabs of civil air defense zones shall be fitted with pre-embedded blast-proof airtight sleeves in accordance with Atlas 07FS02 for civil air defense water works. Gravity drainage pipes are prohibited from passing through partition walls and roof slabs of civil air defense zones.
Installation of explosion-proof floor drains shall comply with the provisions of Atlas 07FS02 for civil air defense water works. Attention shall be paid to the thickness of the post-cast building layer and accurate elevation control during installation. After installation, drain covers shall be removed and stored separately. The interior of floor drains shall be fully and compactly filled with woven bags stuffed with wood chips to prevent clogging. Drain covers can be reinstalled after the completion of building floor construction.
Concealed electrical conduits in civil air defense zones shall adopt hot-dip galvanized steel pipes with a wall thickness of no less than 2.5 mm. Electrical pipelines passing through civil air defense partition walls and roof slabs shall undergo blast-proof airtight treatment as specified in Atlas 05SFD10 for civil air defense electrical works. Exposed conduits shall be equipped with pre-embedded airtight sleeves for crossing partition walls and roof slabs, and the construction details of such sleeves shall follow Atlas 05SFD10 for civil air defense electrical works.
Standby reserved pipes such as signal pipes and detection pipes penetrating blast walls for wartime use shall also be properly arranged.
For air ducts to be installed in civil air defense zones during wartime, reserved pipes complying with airtight requirements shall be pre-embedded along with structural construction at positions where ducts pass through blast walls. Comprehensive layout coordination shall be conducted by verifying dimensions, coordinates and elevations of reserved pipes against drawings of all disciplines to avoid pipeline conflicts. All reserved pipes for civil air defense ventilation shall conform to relevant civil air defense codes.

III. Airtight Construction Methods for Pipelines Penetrating Blast Walls

Steel plates with a thickness of 3 mm to 4 mm shall be used to fabricate airtight flanges for electrical steel conduits, which shall be firmly welded to structural steel bars.
Rigid flame-retardant plastic electrical conduits shall be fitted with airtight flanges made of plastic plates of the same material, with a plate thickness greater than 5 mm.
Steel pipes for ventilation ducts shall have a wall thickness of no less than 3 mm. The airtight flange shall be 5 mm to 6 mm thick, and the pipe section extending out of the wall shall be 100 mm in length.
Pre-embedding of airtight sleeves for civil air defense works

Blast-proof airtight sleeves shall be pre-embedded at positions where water supply inlet pipes, drainage outlet pipes, vent pipes, oil supply pipes and fire water supply pipes penetrate walls and floor slabs of civil air defense structures.

For short airtight wall-penetrating pipes of water supply pipes and pressure drainage pipes, hot-dip galvanized steel pipes with a wall thickness over 3 mm shall be used. Airtight flanges shall be made of steel plates with a thickness of 10 mm to 12 mm. The steel plates shall be flat, and the flange height shall be 30 mm to 50 mm. Weld joints between airtight flanges and short wall-penetrating pipes shall be full, uniform and tight.

Fixed flanges at both ends of short airtight wall-penetrating pipes shall be constructed in the same manner as airtight flanges. The outer surfaces of the fixed flanges shall be flush with the wall surface.

Airtight flanges shall be installed at the mid-thickness of walls and firmly welded to surrounding structural steel bars. The central axis of short airtight wall-penetrating pipes shall be perpendicular to the wall surface.

Reservation of structural openings

Fully review construction drawings and check the consistency of reserved openings shown on architectural, structural and installation drawings. Integrate all opening information into unified structural opening drawings to avoid conflicts caused by separate drawing submission by different disciplines.

Collect technical data of large electromechanical equipment according to design documents, and verify whether the dimensions of hoisting openings, embedded parts and load-bearing capacity meet the hoisting requirements of large equipment.

Complete detailed layout design for reserved openings at densely piped areas such as electrical shafts and water pipe shafts, as well as key positions including civil air defense openings prior to structural construction, and produce detail drawings for shaft openings.

Conduct regular inspections during the binding of structural steel bars, and remind construction personnel to reserve openings in a timely manner. Before formwork erection after steel bar work is finished, fully check whether the positions and elevations of all reserved openings are consistent with drawings. Promptly notify civil engineering management staff to rectify any defects found, and conduct re-inspection to confirm compliance after rectification.

IV. Pre-embedding for Installation of Key Civil Air Defense Components

Pre-embedding and installation of explosion-proof floor drains and associated pipes

Explosion-proof floor drains are generally installed in gas-proof passages, airtight passages, simple decontamination rooms, gas filter rooms and diffusion chambers.

Pre-embedding and installation of explosion-proof floor drains and drainage pipes shall be carried out before pouring the basement floor slab or building bedding layer. The floor surface of relevant rooms shall be sloped towards floor drains at a gradient of 0.5%. Since explosion-proof floor drains are connected to drainage pipes via threaded joints, galvanized steel pipes must be adopted for drainage pipelines.

Three common models of explosion-proof floor drains are available: FBFDD50, FBFDD80 and FBFDD100, with nominal outlet diameters of DN50, DN80 and DN100 respectively.

Pre-embedding and installation of explosion-proof overpressure automatic exhaust valves and sleeves

Explosion-proof overpressure automatic exhaust valves are usually installed in gas-proof passages or simple decontamination rooms.

After steel bar binding for basement walls is completed, short pipes fitted with airtight flanges shall be pre-embedded at designated positions. Such pipes shall be rolled from 3 mm thick steel plates with an outer diameter of 250 mm, and coated with two layers of anti-rust paint.

Connecting flanges and reducing pipes shall be welded on during basement decoration. All joints shall be airtight, and flange surfaces shall be kept vertical. During valve installation, the opening direction of the explosion-proof overpressure automatic exhaust valve shall face the exhaust direction, and the valve lever shall remain plumb.

Pre-embedding and installation of pressure measuring pipes

DN15 galvanized steel pipes shall be pre-embedded in blast-proof airtight walls of civil air defense basements to serve as pressure measuring pipes.

The indoor ends of the pipes shall be connected to pressure measuring devices inside the wartime fan room.

The outdoor ends shall extend into passages or vertical air shafts outside blast-proof airtight structures. Pipe orifices shall face downward and be equipped with anti-clogging measures.