Purple Book (Guide for Controlling ACM in Buildings) Part 9 PDF

Figure 11. An asbestos removal project. 5-5 to outside the building will provide added protection in case of an accident. Appendix J summarizes specifications for negative air systems. ● ● ● When containment barriers are dismantled after ACM removal, the sealing tape used to attach the plastic...

Figure 11. An asbestos removal project. 5-5 to outside the building will provide added protection in case of an accident. Appendix J summarizes specifications for negative air systems. ● ● ● When containment barriers are dismantled after ACM removal, the sealing tape used to attach the plastic sheets to walls and ceilings frequently removes paint. It is prudent to include the cost of repainting all walls (and ceilings, if appropriate) in estimates of asbestos removal costs. Asbestos waste is sometimes spilled both in and outside the work area. Containers full of wet material are very heavy and hard to transport. These containers must be sealed and handled carefully. Workers should continue to wear protective equipment during these operations. Also, disposal sites may be scarce. Some states require a disposal permit before removal begins. Amended water (water and wetting agents) from spray operations may leak through the polyethylene sheets and damage floors, especially tile and wood. Sealed double plastic sheets should protect the floors. When removal and disposal operations are finished, evaluate the need for a sealant on the exposed surface. (The need to reinsulate or resoundproof with asbestos-free materials should be decided before removal begins.) Sealants generally are necessary where the underlying surfaces are porous (for example, concrete blocks or slabs), since a few fibers usually remain after removal. Cost of asbestos removal varies widely by region and by job. Where the underlying surface must be sealed and the ACM replaced, those costs must be added to removal costs. 5.1.2 Enclosure Enclosure involves construction of airtight walls and ceilings around the ACM, Figure 12 shows a typical enclosure, These recommendations for constructing enclosures should be followed: 3 ● To reduce fiber release, drills used during installation should be equipped with HEPA-filtered vacuums. ● Underlying structures must be able to support new walls and ceilings. ● New construction material should be impact-resistant and assembled to be airtight? Gypsum panels taped at the seams, tongue-and-groove boards, and boards with spline joints all qualify. Suspended ceilings with lay-in panels are not acceptable. Joints between walls and ceilings should be caulked. ● If lights are recessed into ACM, they must be removed carefully to minimize fiber release. Lights should be reinstalled beneath the new ceiling. ● Relocation of plumbing lines and computer cables may be necessary. ● Building records must note the presence of asbestos behind the enclosure to prevent accidental fiber release during remodeling or building demolition. (The presence of ACM should have been documented as part of the special O&M program.) Signs should be posted, noting that ACM is behind the enclosure. No enclosure will be totally airtight. The practices recommended here are designed to greatly reduce air movement across the enclosure boundary. 5-6 After enclosure Before enclosure Figure 12. An asbestos enclosure project. 5-7 5.1.3 Encapsulation with Sealants Encapsulation refers to the spraying of ACM with a sealant. The sealant should bind together the asbestos fibers and other material components and offer some resistance to damage from impact. Figure 13 shows an asbestos encapsulation project. Encapsulation should be used only on granular, cementitious material—commonly known as acoustical plaster. A sealant should penetrate the ACM and adhere to the substrate (or form a tough skin over the material), withstand moderate impact, be flexible and flame-retardant, resist deterioration over time, and be non-toxic. EPA evaluated over 100 sealants, using five criteria: impact resistance, flame spread, smoke generation, toxic gas release during combustion, and adhesive/cohesive strength (USE PA 1981). The American Society of Testing and Materials (ASTM) also is developing laboratory testing criteria for sealants. Additional information on the EPA sealant study can be obtained from EPA’s Office of Toxic Substances, TSCA Assistance Office (see Appendix E for phone numbers). Although the EPA study can help building owners choose a sealant, its effectiveness on the particular ACM should still be tested on-site over several days. (ASTM is developing criteria and procedures for such on-site tests.) Do not encapsulate material that is delaminated or deteriorated, or that shows extensive damage. If delaminated, the material will be pulled down by the additional weight; if deteriorated, the ACM may be blown off by sealant application; if extensively damaged, the material may be repeatedly abused and the sealant will not hold up. The condition of the sealant on previously encapsulated materials also should be inspected. Reapplication of sealant may be necessary. Latex paint has been used as a sealant for granular, cementitious materials. Select a brand with a high vehicle content (at least 60 percent by weight) and at least 25 percent by weight vehicle resin.4 For encapsulating ACM, apply paint considerably thicker than recommended for painting. Coverage should be no more than 100 sq. ft. per gallon, and should create a continuous, unbroken coating. Apply sealants with airless spray equipments One recommended method is to apply a light (mist) coat, then a full coat applied at a 90 degree angle to the direction of the first. If latex paint is used, the full coat can also be applied by roller before the mist coat dries. Record the type of sealant used and the nature of the material and substrate encapsulated. This information is needed to avoid unintentional release of fibers during later remodeling or demolition. 5.2 Abatement Methods for Pipe and Boiler Insulation Abatement methods for ACM used to insulate pipes, boilers, ducts, tanks, and related equipment are somewhat different from methods for asbestos sprayed or troweled on surfaces. When damage to pipe or boiler covering is limited, repair is the recommended abatement approach. Non-asbestos plastering can restore open joints, wrapped or plastered areas that are damaged, and areas around valves and flanges. Encapsulant can also be used as a temporary measure. Do not use duct tape; it becomes brittle after exposure to high temperatures. Where large portions of pipe and boiler insulation must be removed, erect containment barriers and employ the full range of worker protections (see Section 5.1). Containment bags may be used instead of constructing containment barriers around the work area. These bags are available commercially. As shown in Figure 14, the bags are positioned around the pipe insulation to be removed, and sealed to the pipe with tape. 4 Paint constituents appear on the label of the can. 5 The use of respirators is recommended for applying any sealant. Solvent-based (as compared to water-based) sealants may require the use of a supplied air (Type C) respirator due to hazards from the solvents. 5-8 Figure 13. An asbestos encapsulation project. 5-9