Due to its strength and versatility, asbestos was woven into thousands of construction products across cities such as Buffalo, Rochester, and Syracuse, New York. However, its respiratory health risks eventually led to strict regulations by the late 20th century. While most building owners know to conduct inspections and abatement on popcorn ceilings, floor tiles, or pipe insulation, asbestos can hide in far less obvious places. These obscure asbestos-containing materials (ACMs) often go unnoticed until a renovation or demolition disturbs them, releasing microscopic fibers into the air.
In buildings constructed between the 1930s and 1980s (and even later due to imported materials), contractors added asbestos to everything from sealants to electrical components. The EPA estimates over 3,000 products historically contained it. While many common uses are well-documented, the overlooked ones pose unique risks because they’re embedded in systems we rarely inspect. Disturbing them without proper testing and abatement containments can turn a routine DIY project into a hazardous exposure event. Let’s discuss the most overlooked ACMs still lurking in homes, offices, schools, and commercial structures today.
1. Window Putty, Glazing Compounds, and CaulkingOne of the stealthiest offenders is asbestos-laden window putty—the grayish, dough-like sealant around glass panes in old wood, metal, or steel-frame windows. Manufacturers added asbestos for fire resistance, strength, and to prevent cracking under thermal expansion. It was especially common in homes built before the 1970s and even in naval vessels for the same heat-resistant qualities.
Look for it in the putty beds holding single-pane glass or sealing window frames to brick, wood, or concrete. Over decades, it dries, cracks, and crumbles—becoming friable and prone to releasing fibers when you replace windows, scrape paint, or chisel it out. EPA guidance notes that although intact putty is low-risk, disturbance during abatement or demolition requires regulated handling. Homeowners replacing vintage windows often discover it the hard way, especially in mid-century bungalows or industrial lofts.
2. Electrical Panels, Switchboards, and Circuit Breaker ComponentsFlip open the breaker box in many pre-1990 buildings, and you might be staring at asbestos. Asbestos was used in panel partitions, arc chutes (the baffles that extinguish electrical arcs), backing boards, insulating cloth, and even the molded bases of circuit breakers. Its non-conductive and heat-resistant properties made it ideal for preventing fires in high-voltage systems.
Switchboards and meter panels in older buildings often feature dark brown or black asbestos-cement boards. Electricians working on upgrades or replacements face the highest risk, as removing panels or wiring can disturb fibers. These aren’t the flashy “popcorn” hazards—they’re behind the scenes in every electrical upgrade.
3. HVAC Flexible Connectors, Vibration Dampeners, and Duct Fabric ConnectionsYour building’s air handling system may harbor another hidden culprit: flexible fabric connectors. They’re also called vibration dampeners or expansion joints, and they link rigid ducts to fans or equipment. These canvas-like or corrugated materials were reinforced with asbestos cloth or felt to withstand movement, heat, and fire. Also on the list: boiler breeching insulation, tank casings, and thermal taping compounds around furnaces. In commercial buildings or older multifamily homes, these components sit in attics, basements, or mechanical rooms. They look like ordinary fabric or cardboard until they’re disturbed during HVAC retrofits. Cooling towers in larger facilities sometimes incorporated asbestos panels as well. The fibers stay bound until cutting or tearing begins.
4. Asbestos Millboard, Paper, and Heat Shields Around Fireplaces and StovesFireplaces and wood-burning stoves from the 1930s-1970s often featured asbestos millboard, corrugated paper, or heat shields as protective barriers behind or around the unit. These thin, rigid sheets (sometimes called “Permaboard” or “Flexboard”) prevented heat transfer to walls and floors. Asbestos paper or blankets wrapped flues or served as gaskets.
Vermiculite-based fireplace decorations or loose-fill attic insulation nearby can also be contaminated. Homeowners restoring historic hearths or installing inserts frequently encounter these during demolition—materials that blend seamlessly with the masonry until pried apart.
5. Chalkboards, Laboratory Hoods, and Fume Hood LinersIn schools, universities, and older labs, asbestos appeared in surprising spots: the backing or adhesive of chalkboards, and the liners or countertops of fume hoods. Acoustical plaster, decorative finishes, and even laboratory tables incorporated it for durability and fireproofing.
Fume hoods in science classrooms or hospital labs used asbestos panels to contain chemical reactions and fires. Wall penetration packing materials (stuffing around pipes or conduits) and spackling compounds in these spaces add to the list.
6. Transite Flue Linings, Vents, and Hidden Cement ProductsTransite (asbestos-cement board) isn’t just for siding or roofing. It was molded into chimney flue linings, HVAC ducts, vents, and even landscape edging or waste lines. In older homes, transite pipes or panels hide in walls, ceilings, or crawlspaces as exhaust pathways.
Base flashing on roofs, felt underlayment, and caulking/putties around wall penetrations complete the picture. These materials are durable but become friable when sawn or broken during plumbing or roofing work.
7. Elevator Brake Shoes and Equipment PanelsBuildings with elevators (common in apartments or offices built pre-1980) may have asbestos in brake shoes, equipment panels, and hoistway linings. The friction-resistant properties made it perfect for stopping heavy cars safely. Modern upgrades rarely trigger full inspections, leaving fibers dormant until a major retrofit.
Other wall and ceiling adhesives that sporadically test positive include stud mastic, ceramic tile glue, and panel mastic. These glues were often used as an extra precaution to maintain stability, even if the walls or panels are also nailed in.
10. Sink Undercoatings
The undersides of many older sinks have a mastic or coating on them, chiefly for the purposes of preventing condensation and sound dampening. Much like other mastics mentioned on this list, these coatings sometimes contain small amounts of asbestos. It’s one of the most overlooked types of asbestos-containing materials in any building.
Why These Matter—and How AEG Can Help The obscurity of these materials is their danger. Unlike obvious insulation, they’re integrated into functional systems we take for granted. Fibers become airborne only when disturbed, but routine maintenance (window replacement, electrical work, HVAC servicing) can trigger exposure.
Testing is essential: hire a certified asbestos inspector before any renovation. If the materials test positive, licensed abatement contractors use wet methods, HEPA vacuums, and containment to handle them safely. DIY removal is illegal in many jurisdictions and extraordinarily dangerous.
The good news? With proper identification and abatement, these hidden hazards can be neutralized. Your lungs—and future occupants—will thank you. If you suspect asbestos in your building, consult local environmental health departments or certified professionals immediately.
Apex Environmental Group (AEG) has six certified asbestos inspectors who conduct investigations and testing on commercial, residential, and industrial buildings. They also have three certified abatement project designers to help formulate the optimal plan for removal.
AEG offers its asbestos services throughout New York State, including but not limited to the following areas: